GB2064851A - Automatic music writer - Google Patents

Abstract

A method of producing a visual representation in musical notation of a musical rendition on a keyboard comprises deriving from a keyboard on which the rendition is performed electrical signals in digital code indicative of the keys operated and the duration of each key operation, processing the signals mathematically to match them to a predetermined format of musical notation and using the signals so processed to operate visual display means, which may be either electronic picture display means or print-out means, to produce a visual display of the musical notation representing the rendition. Apparatus for carrying out the method may include means for generating a rhythm structure to which said rendition is to be matched, sound producing means for producing audible signals corresponding to the keyboard rendition and indicative of said rhythm structure. The mathematical processing of said signals e.g. by a computer includes the rounding of numbers representing said key operations to fit a numerical structure representing a predetermined time pattern, in accordance with a selected precision factor. <IMAGE>

Description

SPECIFICATION Improved method of and apparatus for inscribing music This invention relates to a method of and apparatus for inscribing music. More particularly it concerns apparatus for inscribing music in normal musical notation directly and automatically from a keyboard rendition thereof.

The invention is based upon a method of analysing a musical rendition to determine the pitch, duration and phrasing of the notes and the use of such an analysis to control visual display means. The visual display means may be of a "transient" nature as for example on an electronic picture tube or in the form of a print-out or "hard copy" representation of the music in normal musical notation.

Apparatus of the kind to which the invention relates finds application in the writing of music by a composer, in orchestration, for transposing keys and soon, and enables the operator to apply to paper in standard musical notation the musical forms which he generates on a keyboard which can be in the conventional form of a piano keyboard. There should be provision for the editing of the written material by modification, addition and deletion of notes, note values and playing instructions. Additionally means may be provided for adding alpha-numeric information to the musical score produced by the apparatus.

Preferably the apparatus will include means for giving audible feedback to the operator to enable him to monitor the musical text as it is generated and preferably he will be provided with an electronic visual display unit so that he can check the graphical representations visually before they are rendered into hard copy, as is the practice in word processing machines based on computer techiques. The machine may include means such as a metronome for providing to the operator a time base to which his performance should be matched in order to enable the machine to interpret the rendition on the keyboard into the format of normal musical notation.

According to the invention in one aspect a method of producing a visual representation of a musical work in musical notation comprises performing a rendition of said work on a keyboard, deriving from said keyboard signals representing in digital code the pitch and the duration of each note of said rendition, processing said signals mathematically to match them to a predetermined format of musical notation and producing from said signals as so processed a visual representation of the musical notation representing said work.

According to the invention in one form a method of producing a visual representation of a musical rendition in musical notation comprises setting up a periodic time base to which said rendition is made substantially conformative, identifying within said time base a rhythm structure, deriving from said rendition signals in digital code indicative of the pitch, times of commencement and times of termination of individual notes of said rendition, modifying said signals to match said rhythm structure, employing the modified signals to identify the values of said individual notes in terms of said time base and generating a visual representation of said values in musical notation.In carrying out this method according to the invention said signals may include digitally encoded representations of the times of occurrence of the commencements and terminations of notes of said rendition on a time scale consisting of subdivisions of the periodicity of the time base and the rhythm structure comprises a selected grouping of said subdivisions to provide a pattern of time intervals within each period of the time base. The signals may be modified by mathematical processing of their digital content to generate modified signals representing the sequence of events produced by the rendition displaced in time to conform to said rhythm structure.

The invention in another aspect resides in apparatus for generating a visual representation of a musical rendition in musical notation comprising a keyboard, means connected to said keyboard for deriving signals therefrom in response to a rendition on said keyboard, electronic computer means for processing said signals to provide an analysis of said rendition conformative to a predetermined time pattern representing a rhythm structure and for interpreting said analysis in terms of musical notation and display means for generating a visual representation in musical notation from the signals so processed.

The apparatus according to the invention may comprise means for sensing the state of operation of the keys of the keyboard, means for periodically scanning said sensing means, primary computer means for detecting changes in the states of keys of said keyboard from one scan to the next and encoding and storage means for encoding and storing information representative of the timings of said changes on a time scale related to said predetermined time pattern.According to a feature of the invention main computer means are provided for deriving digitally encoded information from said encoding and storage means, mathematically adjusting said information to render it conformative to said predetermined time pattern, interpreting the events represented by the information so obtained in terms of musical notation and employing the information so interpreted to generate a visual representation of said musical notation.

According to a further feature of the invention the primary computer means may be arranged to compare the state of a key as detected by said sensing means with the state of the same key as previously recorded in said storage means and if a change of state is revealed by such comparison to record the new state in said storage means and feed a signal signifying the changed state of said key to said main computer means.

According to yet another feature of the invention the apparatus according to the invention includes means for generating time base signals representing a time base to which a rendition on the keyboard is to be made conformative.

According to a feature of the invention an apparatus for generating a visual representation of a musical redition in musical notation includes sound producing means connected to generate sounds representative of the rendition on said keyboard. Said sound producing means may be in the form of sound synthesising means adapted to synthesise sounds in accordance with information derived from the main computer means.

According to a further feature of the invention the sensing means associated with the keyboard comprises means for sensing the rest position of a key and means for sensing the operated position of a key and said primary computer means is arranged to generate digitally coded information indicating the times of departure from and restoration to said rest position and said operated position. According to a preferred feature of the invention the primary computer means is arranged to supply interrupt signals to the main computer means only in response to a sensed movement of a key from the rest position into the operated position or vice versa.

Other features of the invention will emerge hereinafter.

In order that the invention may be more clearly understood it will now be described with reference to the accompanying drawings in which: Figure 1 is a schematic representation of an apparatus according to the invention; Figure 2 is a diagram illustrating the operation of the method according to the invention; Figure 3 shows the musical notation set up by the process described by reference to Figure 2; Figure 4 is a schematic diagram illustrating the circuit of the keyboard primary computer; Figure 5 is a waveform diagram showing the sequence of events in the keyboard primary computer; and Figure 6 is an explanatory diagram illustrating a feature of operation of the keyboard primary computer of an apparatus according to the invention.

The apparatus represented schematically in Figure 1 comprises a keyboard 1 which conveniently takes the form of a piano keyboard but which is furnished with contacts associated with each note of the keyboard by means of which signals may be applied to a controller 2 which in turn feeds a main computer 3. The controller 2 includes a primary computer which serves to generate output signals from the keyboard representing the key operations and command signals by which the operator can control the operating characteristics to which the apparatus is required to operate and will become apparent hereinafter.

While the keyboard contacts may be simple contacts giving simple "on" and "off" information to the controller they are preferably multiple contacts consisting of two or more contacts which make contact selectively as the key is pressed so that the controller is fed with information indicative of the speed with which the keys are struck. They may alternatively or in addition be made pressure sensitive so that a sense of "touch" will be given.

The main computer is connected to a computer store 4 and is provided with peripheral equipments in the form of a visual display unit 5 and a printer 6. A sound producing equipment 7, the nature of which will be described more fully below, is connected both to the keyboard 1 and the controller 2 to provide a sound output for the purposes to be described below.

The arrangement is so organised that notes played on the keyboard 1 are processed by the computer 3 so as to provide either a visual display on the visual display unit (hereinafter referred to as the VDU) 5 or a print-out on printer 6 or both a visual display and a print-out. Signals for operating the VDU 5 and the printer 6 may also be drawn from the store 4 under control of the main computer. The sound box 7 serves two functions. Firstly it may be used to provide a beat in the manner of a metronome in order to set up a time base or rhythm by which the keyboard operator may adjust the speed of his playing to enable the computer to analyse the notes rendered on the keyboard into a predetermined format of musical notation.

This beat may take the form of a single beat marking the commencement of each bar, or may also include the individual beats within the bar so as to give the complete rhythm. In this latter case the sounds representing the beats within the bar are preferably distinguishable from those marking the bar commencements by being different in pitch or length or in some other way, thus giving an audible pattern such as may be written "Tum-ta-ta, Tum-ta-ta " for 3-4 time, or "Tum-ta-ta-ta-, Tum-ta-ta-ta- " for 4-4 time, for example.

The other function of the soundbox 7 is to provide an audible feed back to the operator indicating the notes which he has played on the keyboard.

In order to be able to print or display the musical notation of the notes played on the keyboard it is necessary to analyse accurately the intended note values and their time placement within the bar or measure.

The difficulty of doing this is that no human being is capable of playing the music on a keyboard in an absolutely precise way, conforming precisely to the theoretical note values and intervals. Notes that should be sounded at the same moment will generally in practice be sounded a minute fraction of a second apart. A note that should be struck exactly at the beginning of a particular time interval in the bar will probably be a fraction of a second too early or late. A note that should be held for, say, 41 of a bar will in practice vary considerably from this interval. The length of bars or measures (i.e. the time taken to play each bar) will vary by fractions of a second, and may at any stage be slowing down or speeding up.

The result of the "raggedness' described above is that the analysing device is presented with a bewildering series of events in time, very few of which are simultaneous, and which have little or no discernible regularity in their overall pattern. It has no means of differentiating between the intentional and unintentional differences in note values and in time intervals.

Confidently and accurately to assign the intended note values and their time of sounding in the bar, is extremely difficult on this basis, and the notation so obtained would be infinitely more complex than intended, and therefore incorrect.

The invention is directed to a method of overcoming these difficulties. Before beginning a passage, or at any time during a rendition at which any change in the parameters is required the operator enters into the controller 2 by way of a switchboard (which may be combined with the playing keyboard) two parameters or "factors" against which the rendition is to be matched for conversion into musical notation.

The first factor specifies the speed at which the bars are to be played, e.g. 30 bars per minute. If the passage is not intended to have bars or measures, the speed can be entered as, say, 120 crotchets per minute.

The second factor specifies a "precision factor" for the passage which is to be played. This factor represents the smallest time interval that is intended to be employed in the coming passage. For example, if the operator entered 1/8 it would indicate to the controller 2 that one-eighth of a bar is the minimum time interval for any note or rest. Any events that occur within this fraction of the bar (i.e. striking, holding or releasing of keys) will be deemed by the controller to have been intended as simultaneous.

The analysis now begins. The controller 2 gives the "beat" to the operator either by an audible click from the soundbox or as a visual pulse displayed on the VDU or both may be given. The frequency of the beat is determined by the "speed" factor entered by the operator as the first parameter. This beat ensures regularity from bar to bar, and ensures that the controller and operator are broadly synchronised.

As an alternative the operator may elect to set the rhythm himself by tapping a foot or making sounds with his mouth or in any other way. For example a foot switch could be provided which the operator would tap to give a signal indicating the bar intervals or a microphone can be arranged to pick up the sound of a foot tapping or a mouth sound. If such an arrangement is used it will normally be preferred to dispense with any audible signal fed back by the apparatus.

As the keyboard is played the controller registers the identity of each note played. To determine from the "ragged" intervals and note values (durations) being played, their true or intended values the controller employs the "precision" factor. No interval or note value can be less than this precision factor, and the controller rounds them accordingly. In the example given, all events occurring within a given 1/8 of a bar are deemed to have been intended as simultaneous. Thus the controller is able to arrive back at the intended note values and intervals, assuming only that the operator's playing conforms reasonably to the theoretical values.

Thus, the unavoidable "raggedness" of the playing of the notes - compared to their theoretical value although matched by the operator as far as can be to the beat sent out by the controller needs then to be finally smoothed by the controller's rounding of the fractional time differences of events according to the pre-defined "precision factor" for the passage.

The manner in which the signals generated by keyboard 1 are rounded into the precise form required for producing a visual indication or print-out of the musical notation is illustrated in Figure 2. This follows the stages by which a bar of music is processed. The bar consists first of a chord GAC of one-quarter bar duration, followed by the single note B of one-eighth bar duration. This is followed in turn by a rest of one-eighth bar and then by the single note G also for one-eighth of a bar followed again by note F for the remaining one-half bar. This note F is shown extended into the next bar into which is extends for one-eighth of a bar.

The rendition of this bar of music by the operator is illustrated in Stage I of the diagram of Figure 2. Let us suppose that the speed factor fed into the controller before the passage commenced demanded a speed of 30 bars per minute. In addition let us suppose that the "precision factor" set by the operator was one-eighth, that is to say one-eighth of a bar. It follows that the duration of one bar is two seconds and the time for one-eighth of a bar is one-quarter second. With these factors set, the operator will be given, say, an audible bleep from the soundbox once every two seconds.

Now, according to the diagram the operator strikes the chord of GAC striking note A a little ahead of the commencement of the bar and notes C and G in that order slightly after the commencement of the bar but both within the first one-sixteenth of it, that is to say within one-eighth of a second from the commencement of the bar. Then the diagram shows that the operator releases the three keys in the order A and C together, and G slightly later, but within the first quarter of a bar and within the first half second of the bar. The operator is slightly late with note B and strikes it after the end of the quarter of the bar but within the next one-eighth second. He releases it, a quarter of a second later. His next note G is then commenced slightly after seven-sixteenths of the bar, that is to say a little before the one second interval or half the bar.He releases it a little after five-eighths of the bar that is to say after one and a quarter seconds and is a little early with note F which he strikes shortly before the one and a quarter second mark and he holds it until a little after one-eighth of a second beyond the end of the bar. These timings are illustrated in the diagram by the horizontal lines which indicate the durations of their respective notes correspondingly lettered.

Stage III of the diagram shows the analysis of these events by the computer. The commencements of the notes C and G both being within the first one-sixteenth of the bar and therefore less than half of the one-eighth precision factor late are rounded by the computer program forward in time so that the three notes GC and A are deemed to have been struck simultaneously. The terminations of the three notes are all within the second half of the second one-eighth bar and are therefore rounded back in time by the computer program so that they all terminate at the end of the first quarter bar. Note B which was struck within the first half of the third one-eighth of the bar is rounded forward to commence at the same time as the termination of the first chord.Since it terminates within the first half of the fourth one-eighth beat it will be rounded forward in time to terminate at one-eighth of a bar duration. Note G was struck in the second half of the fourth one-eighth bar period. It will therefore be rounded back to the half-bar mark that is to say after a one second interval from the commencement of the bar. Similarly since its termination is within the first half of the sixth one-eighth bar period its termination will be rounded forward to terminate at the end of the fifth one-eighth bar period. Finaliy, the commencement of note F which occurs in the second half of the fifth one-eighth bar period will be rounded back to commence at the end of the fifth one-eighth bar period.Since it extends beyond the bar into the second half of the first one-eighth of the ensuing bar its termination will be rounded back to the end of the first one-eighth bar period of the next bar.

The musical interpretation sequence which the machine is required to set down in musical notation is therefore as follows: 1. The chord of GAC commencing on the first beat of the bar and sustained for half a second that is to say one quarter of the bar.

2. The single note B sounded at the commencement of the second quarter of the bar and sustained for one-eighth of a bar.

3. A one-eighth bar rest.

4. The single note G sounded at the half bar mark and sustained for one-eighth bar.

5. The single note F sounded at the five-eighths bar mark and sustained into the next bar over one-eighth of that bar.

The signals representing this sequence of notes can then be passed to the memory 4 to be stored for further use either as a visual display or for operation of the printer 6. The memory unit 4 holds the program data for supplying to the VDU 5 and the printer 6 the appropriate signals to set up the display on the VDU 5 or operate the printer 6. Similarly signals from the memory unit 4 can be called out by the computer and fed to the controller 2 to supply back to the soundbox 7 such recordings as have previously been made. This enables the operator to superimpose new material on the previously recorded music and/or to edit the earlier recording as may be required. These operations can be monitored by the operator by means of the display simultaneously provided on the VDU 5.The computer program provides for the edited version to be fed back into memory 4so that it can be recalled at will for further editing or for the addition of further material or for the purpose of producing a print-out on printer 6.

The musical notation of the passage set up as above described is shown in Figure 3. The note values, crotchet for the first chord, quavers for the second and third notes, dotted crotchet for the fourth note and quaver for the first note of the following bar, as well as the bar lines, the "rest" sign and the tie between the dotted crotchet and the quaver in the next bar will all be selected automatically by the main computer by interpretation of the key operations. The appropriate print-out signals will then be demanded by the computer from store and fed to the print-out machine andior the VDU. These are computer program operations and need not be further described.

The nature and functioning of the controller 2 will now be further described by reference to Figures 4,5 and 6 of the accompanying drawings. Referring first to Figure 4 this shows in block schematic form the electrical circuitry by which signals are generated to feed to the computer the information it requires to enable it to carry out the analysis of the keyboard operations and interpret these in a form suitable to set up a visual representation of the keyboard rendition in musical notation.

The operations of this circuit are controlled by a synchronising clock circuit 10. This contains an oscillator generating a basic frequency of, say, 1 megahertz which by a sequence of count-down circuits generates a square wave having a periodicity appropriate for the repetitive scanning operation by which the keyboard operations are detected and timed.

Signals from the synchronising circuit 10 are applied to a counter 11 which generates repetitively an output in the form of a seven bit 'address'. As the count in counter 11 progresses under the effect of signals from the synchronising circuit 10 it identifies cyclically each of 128 states which are used to activate in turn the contacts of the keyboard. Not all of these keys will be required for the notes of a musical instrument.

Assuming an 8 octave keyboard is to be simulated 24 keys will be available for other purposes and can be used to key into the system special instructions such as the time signature, the key signature, the intended speed, any preliminary instructions, such as pianissimo, fortissimo and the like, as may be required. The seven bit 'address' is decoded in a decoder 12 so as to carry out a sweep of the 128 moving contacts of the keyboard and activate them in turn. In the present example the complete array of 128 moving contacts will be scanned in about 1 millisecond and a period of about 8 microseconds is allocated to each key. Of this 8 microseconds 2 microseconds are used for the reading of each key state and the remaining 6 microseconds are then available for the settling of signals generated by the contacts of the keyboard.

Each of the key contacts of which only 3 are shown in the drawing has two possible positions, one the upper or resting position in which it connects to the circuit indicated generally as A, and a bottom position in which it makes contact with circuit B. There is also an intermediate position in which neither circuit A nor circuit B is contacted. The time which the key contact takes to move from its top position to its bottom position can vary considerably according to the manner in which the key is operated. It is expected that it might vary between 5 milliseconds for a fast movement and 25 milliseconds for a slow movement. This variation of operating time can be used to provide an indication of the strength with which the note is to be struck and therefore of the loudness required in the rendition.However, it will be seen that the period of a complete scan of the keyboard is only about 1/5th of the time taken for the fastest operation of the key so that a number of scans will take place during the operation of a key and the various events, namely the departure of the contact from its top position, its passage through its mid position when it is not connected to either contact and its arrival at the bottom contact will cover a number of scans and the various events will be separable one from the other by the subsequent circuitry.

As will be seen the top contacts of all 128 keys are connected through inverter 13 to a latch circuit 14 in which the state of the key contact at present under scrutiny by the scan will be temporarily held.

The 128 bottom contacts are connected through an inverter circuit 15 to a second latch circuit 16. In this case however the inverter 15 is connected to the latch circuit 16 through an "Exclusive OR" circuit 17. Thus the latch circuit 16 will be set either by a signal from the top contact or by a signal from the bottom contact of the key currently being scanned but will not be operated if signals are present on neither of lines A and B or on both simultaneously.

The state of latch circuit 14 is fed to and stored in the memory circuit 18, being passed to the appropriate address in this memory by virtue of the seven bit addressing signal applied through bus 19 from the counter 11. Similarly, the state of latch circuit 16 is fed to memory circuit 21 and is similarly addressed. It will be appreciated that the address used in each of these memories represents the current count on counter 11 and is specific to the key which is being interrogated by the scan at the relevant time.

Each of the latch circuits 14 and 16 is also connected through an "Exclusive OR" circuit 22 and 23 respectively to a "First-in-First-out" memory 24 which will be further described below.

Apart from an input from latch 14 the "Exclusive OR" gate 22 receives an input from memory 18. This input represents the state previously recorded in that memory for the key being scanned. The gate 22 therefore delivers an output only if the input from 14 is different from that from memory 18 showing that a change has taken place since the output from the relevant key has changed since the last scan.

Similarly the "Exclusive OR" gate 23 receives an output from memory 21 so that a signal is transmitted through 23 only if a change has taken place in the state of this bottom contact between this scan and the previous scan. The signals from gates 22 and 23 are applied to the "First-in-First-out" memory 24 (hereinafter referred to as the "Fi-Fo" memory) as digits indicating whether a change has occurred in the top contact or the bottom contact of the key in question while the other digit, that applied through gate 23, is used to indicate that a change has taken place at all, that is to say in either one of the contact circuits so as to generate an interrupt in the main computer circuitry.

The seven bit 'address' from counter 11 is also fed to the Fi-Fo memory 24. Since the number arriving over this input to memory 24 is significant of the key being scanned at the relevant moment it is used as a number signifying that key. Any change of state of either a top contact or a bottom contact detected by the circuitry so far described will be stored in Fi-Fo memory 24 as a 7-digit number signifying the key to which it relates and a further bit signifies whether the change is to the top or bottom contact. The memory 24 is of a well-known type which operates to feed each number generated as above described, in turn, to its output.

The output is applied through a buffer circuit 25 to an output port 26 feeding the main computer.

Figure 5 shows in the form of a series of waveform the sequence of events taking place in the keyboard primary computer. Waveform a represents the two microsecond square wave generated by the synchroniser circuit 10. The two microsecond positive phase shown is followed by a six microsecond negative phase.

However all the significant events are triggered by the positive phase shown and it is unnecessary to carry the waveform into its full extent. Waveform b is the same as waveform a but delayed by 500 nanoseconds and can be regarded as a delayed clock signal. The leading edge of waveform a is used to generate a signal which sets the latches 14 and 16 to hold them in the state determined by the key contacts of the switch-board at the moment when the new cycle is to begin. This enables the state of the key contact as it exists at that moment to be compared with the previous state which it occupied at the time of the last scanning cycle and which has been stored in memory 18 or 21. Latch 14 will hold the voltage applied to line A and will therefore signify the state of the top contact of the key, i.e. "made" or "broken".Latch 16 will hold a state (1) signifying that either the top contact is made or that the bottom contact is made, or if the contact is in mid point between its top and bottom positions the latch will receive no signal through the Exclusive OR gate 17 and so will remain unset (0). As will appear later this enables the mid position between the top and bottom contact to be "recognised" in the computer. The 500 nano-second delay between this action and the leading edge of the waveform b, i.e. the delayed clock ensures that the voltages applied to the Exclusive OR gates 22 and 23 properly represent the previous recorded state and the present state of the key contacts derived from memories 18 and 21 and latches 14 and 16 respectively.

The leading edge of the delayed clock can then trigger the Fi-Fo memory to accept the signals through Exclusive OR gates 22 and 23. A signal through gate 23 indicates that a change has taken place since whether there is a signal through A or through B there will be an output from latch 16 to be compared with the stored state from memory 21. If latch 16 has not been set it can only be because the key contact was in its mid position. The absence of a set signal from latch 16 therefore is significant of the mid position of the key contact and any signal derived through gate 23 will in those circumstances signify that the key contact has left either the top contact or the bottom contact and is in the mid position. In other words this part of the circuit ensures that a signal calling for an interrupt in the main computer will be given for any one of the changes which are possible.As to Exclusive OR gate 22 the signal fed through this gate will indicate that the change signalled through gate 23 concerned the upper contact (if the comparison is positive) or that the change signalled through gate 23 concerned the bottom contact (if the signal through gate 22 is negative).

If a signal is passed through gate 23 to the Fi-Fo memory, signifying that an event has taken place, a signal is applied to the Fi-Fo memory (waveform c) which initiates the shift of the numbers stored in the Fi-Fo memory forward so as to clear the Fi-Fo input for reception of the new information. This in turn initiates a signal (waveform d) which indicates that the Fi-Fo is ready to receive the new information and the information is so written in.Termination of the sqaure wave of waveform c triggers another waveform (waveform e) which provides for the writing-in of the informatin into memories 18 and 21 to record the present states of latches 14 and 16 and therefore of the upper and lower contacts of the keyboard to be used as the previous states next time those key contacts are interrogated by the scan. At the end of the two microsecond positive phase of the synchronising waveform (waveform b) the counter 11 is advanced by 1 count.

It will now be seen how the effects of "contact bounce" or indeterminate operation of the key contacts is sorted out by the primary computer. This is illustrated in Figure 6 in which the three "waveforms" indicate three possible modes of operation. In the first diagram the normal and expected mode of operation is illustrated. The top level of the line of the diagram indicates the top position of the key and the bottom horizontal line the bottom position of the key. Point A indicated by the vertical line shows where the top contact is broken as the key contact moves downwardly. Further depression of the key makes the bottom contact at B. This sequence of A being broken and B made is the proper sequence and will be signalled as two separate events of which the computer can take cognisance.Similarly when the key is lifted (right-hand part of diaram) contact B is broken before contact A is made and again a meaningful sequence of events takes place. In the second diagram the case is illustrated of a key not being fully depressed. The second event labelled A in this diagram will be "recognised" by the computer as an error and will cancel the first since both events concerned the state of the upper contact. The third event marked A restarts the timing of a note and when the key is fully depressed so that the bottom contact is made the computer will have the necessary information to "order" the sounding of the note at the right volume and to initiate the recording of the note (first event marked B).At the next event marked B no action is required by the computer but at the final event A the sequence is ended and the computer can then determine what note to show on the VDU and print on the printer. Thus in the first diagram the length of note recorded will be according to the time elapsed between the two events namely the first event marked B and the second event marked A; in the diagram b the note extends between the first B and the final A of the sequence. In diagram c it is supposed that the bottom contact is released without the top contact being made. Since there are no "A" events between the first and fourth "B" events the computer will ignore the second and third "B" events and the length of note sounded will be from the first B event to the final A event.The time between the first A event and the first B event will signal to the computer the volume at which the note is to be played.

The way in which the various events are signalled to the computer is illustrated in the following Table. Key A B A + B Previous Previous C D Comment Position A A + B Top 1 0 1 1 1 0 0 At rest at top. No event.

Mid 0 0 0 1 1 1 1 Leaving top moving down.

Type 1 event.

Bottom 0 1 1 0 0 0 1 Reach bottom moving down.

Type 0 event.

Bottom 0 1 1 0 1 0 0 At rest at bottom. No event.

Mid 0 0 0 0 1 0 1 Leaving bottom moving up.

Type 0 event.

Top 1 0 1 0 0 1 1 Reach top moving up. Type 1 event.

Top 1 0 1 1 1 0 0 At rest at top. No event.

Mid 0 0 0 1 1 1 1 Leaving top moving down.

Type 1 event.

In the Table a "1" in the A column indicates that the top key contact was made, an "0" indicates that the top contact was broken. Similarly in column B a "1" indicates that the bottom contact is made and an "0" indicates that the bottom contact is broken. Column headed A + B indicates the output from Exclusive OR gate 17. There is a "1 " in this column whenever there is a "1" in either column A or column B. In the column headed "Previous A", in the top line it has been assumed that the previous state of contact A was a "1" as read from memory 18. It follows that previous A + B in the next column will be a "1". Columns C and D indicate the signals passed on by gates 22 and 23 respectively.The significance of these signals is given in the right-hand column and it will be seen that when the contacts either at top or at bottom are at rest no event is signalled by the presence of zeroes in both columns C and D. An event affecting the top contact is signalled by "ones" in columns C and D while an event affecting the bottom contact is signalled by the sequence "0, 1".

An input port 27 from the main computer supplies signals to the memory 24 through a decoder 28. A signal thus received from the main computer triggers the supply of the next available number in the memory 24 through buffer 25 to the output port 26 so that the event, whatever it may be, can be acted upon by the main computer. As shown, the signal from the main computer is applied also to the buffer 25 to release the current number to the output port 26 and enable the next available number to be fed from memory 24 into buffer 25 where it is available the next time the main computer is prepared to accept an interrupt. The fact that there is a number in the buffer 25 is sufficient to indicate that an interrupt is being called for and an event has taken place of which the main computer must take cognisance.

It will be understood from the above that the computer is kept fully informed of every event taking place on the keyboard and of the nature of each event. It is of course necessary that the capacity of the Fi-Fo memory 24 should be adequate to store as many events as may occur between the acceptance of an interrupt by the main computer and the next demand for an interrupt. Notionally many events can take place simultaneously at the keyboard. In normal use no more than ten simultaneous events are likely to occur since performance on the keyboard is mainly limited to the ten fingers of an operator. On the other hand the speed of operation of the computer is such that a large number of interrupts can be accepted a time which is very short compared with the operating time of successively struck keys.Nevertheless, sufficient capacity in the memory 24 is preferably provided to allow for abnormal use of the keyboard such as for example playing of a duet with four hands or the simultaneous pressing of a greater number of keys than ten by misuse of the keyboard. To this end one of the surplus key contacts which have been referred to above can be used to supply an error signal to restore the situation if the memory 24 is in danger of being overloaded.

Within the main computer the signals supplied through output port 26 are processed as above described to provide the signals required for either a VDU or printer output. The main computer will contain its own clock against which the time intervals between events on the keyboard are measured. Thus, whenever an interrupt is signalled by the Fi-Fo memory 24 the computer will within its own time accept the information then presented at the output port 26. The timing of this event will be the main computer's own timing but will in normal operation be no later than a millisecond or so from the occurrence of the event in real time.Since the nature of the event is known to the computer, that is to say the key number involved and whether it concerns the top or bottom contact the computer can process this information against its own program to generate whatever signals are required to write up on the VDU or supply to the printer those signals which will generate the appropriate symbols. Assuming that the rendition on the keyboard is continuous and that a continuous succession of beat signals is supplied signifying the beat structure to which the rendition is conformative, the intervals between one event and another can be regarded by the computer as significant.

That is to say they indicate either that a note is sustained (circuit B is actuated) or, more importantly, that a rest between notes is intended (circuit A is actuated). However, if the performer breaks off his rendition and there is delay before he executes the next passage of it the computer will need to be "told" tha this is the situation so that it does not in fact generate a prolonged series of "rests" to be written into the music. To cater for this eventuality the machine can be provided with a "pause" key or pedal which can be used in the manner of the error signal above referred to, to suspend the feeding of signals into the Fi-Fo memory 24 until such time as the rendition is to continue.If the bar beats setting the rhythm of the rendition are generated by the operator himself the computer can be organised to take account of a cessation of such beat signals and operate a "pause" regime automatically. It will be appreciated that if through irregularities of this kind the visual representation of the rendition is made incorrect the errors can be edited out by any suitable editing procedure programmed into the computer.

The computer 3 may take the form of one or more microprocessors furnished with the appropriate programs. Similarly the memory unit 4 can take the form of one or more microprocessor storage units, backed by magnetic tape or magnetic discs being provided to supply the total storage capacity required for the intended operation. Clearly the display on the VDU 5 and print-out on printer 6 will require to be in standard musical notation showing the usual five line stave with clefs, time signatures and so on. The signals for all these representations are stored in the memory unit 4 and can be called into the computer as and when they are required. The symbols provided for in this way will of course include the signs for speed, loudness, crescendo, diminuendo, fortissimo, pianissimo and so on. In order to call these signs from the memory as and when required an alpha-numeric keyboard is required to enable the appropriate fetch signals to be keyed in. This alpha-numeric keyboard can be combined with keyboard 1 or can be a separate typewriter keyboard with the appropriate auxiliary keys to provide for computer control in normal manner.

Apart from the standard terms which will be stored in the memory unit as above described the alpha-numeric keyboard can be used to introduce wordage such, for example, as the words for an aria or song to be printed under the musical text.

The signal formats required for the alpha-numeric data are well-known in computertechique. Similar signal formats can readily be set up for the musical notation. Separate signal formats can be stored for each note value, breve, semi-breve, minim crotchet, quaver etc. or each note can be built up from the required components each separately stored and addressed. For example the outline "dot" required for a minim can be stored and the vertical "tail" stored separately. The two can be brought together by the computer program which, under control of the signals generated by the keyboard will develop the "dot" outline at the appropriate height on the stave and apply the "tail" in the appropriate register on the "dot".The same "tail" signal can then be used, applied to a solid dot, for a crotchet or quaver and the single, double and treble "flags" required to indicate a quaver, semi-quaver or demi-semi-quaver, separately stored, added to the tail as may be required and so on. The program will provide for the duration of a note as derived from the keyboard to be categorised and the appropriate symbols to be brought from store, taking into account any irregularities which may be encountered, such as the intervention of a bar mark being due, on a time basis during the sustentation of a note. Thus in Figure 3 the intervention of the bar mark during the final note F of the phrase will indicate to the computer that the note must be written into both bars and a tie sign imposed.It will also signify that the part of the note in the first bar must be a dotted crotchet, since that is the period of time remaining in that bar and that the part of the note carried over into the next bar is a quaver, since that is the length of note remaining after the end of the first bar. These signal formats are used to control a matrix display or print-out of sufficiently fine structure to provide a build-up of the lines, notes and special symbols required for the notation. Hence the printer unit 6 is preferably of a kind which produces a graphical print-out, on either a line-by-line or matrix basis, or may be a high-resolution plotter.

If a combined muscial and alpha-numeric keyboard is to be used this may be organised in various ways.

Since the primary function of the keyboard will be for the purpose of a musical rendition it is preferred that the keyboard be in the form of a piano keyboard with the "natural" notes as white keys and the intervening half tones interspersed in groups of three and two black keys as is normal. However, by appropriate switching the functions of the keys can be converted to their alpha-numeric purpose and again by suitable switching they can be caused to provide the command signals required by the computer. The markings required to guide the operator in operating the keyboard in these other roles can be provided on the keys themselves or an overlay can be provided to be brought into operation when the function of the switchboard is to be transferred. Alternatively, a separate index board mounted alongside the piano-type keyboard can be used.In yet another arrangement the piano-type keyboard is arranged to be translucent and the alternative functions of the keys can then be displayed by selective illumination from below.

The controller 2 receives signals from the keyboard 1 and from the computer 3. It may in fact be considered as part of the computer in that it is required to interpret signals from the keyboard and feed the appropriate commands to both the soundbox 7 and the computer. The commands to the computer cause the latter to select from the memory 4 the stored signals representative of the symbols to be displayed and/or printed out. The basic rhythm of the system is set by the controller which receives signals from the keyboard in response to interrogations carried out by a scanning operation. The whole contact system of the keyboard is scanned at regular intervals which are short in relation to the "precision factor" above referred to i.e. in the example given every one thirty-secondth of a second, which is one sixty-fourth of a bar.At each scan the contacts operated are sensed so that a signal, timed in relation to the scan and thus identifying the required note is obtained, interpreted as a number and fed to the computer. Thus the commencements durations and terminations of the key operations are identified. More frequent scans may be made if it is required to derive a "touch" interpretation from multiple, sequentially operated contacts as suggested above.

In addition, the controller 2 feeds to the soundbox 7 a signal at regular time intervals so as to trigger the metronome beat at the required intervals representing the appropriate number of scans.

The soundbox 7 may take a variety of forms. Basically it must include a sound producing transducer such as a loudspeaker and preferably includes electronic waveform generators set up in known manner to synthesise the sounds demanded by the operator. In a simple system it may merely provide tones which serve to give feedback to the operator indicative of the performance he is rendering. Such a system may suffice for composition, for example. However, preferably a more elaborate sound synthesising system is provided so that sounds representative of different instruments may be simulated. The required synthesis is made under the control of the controller 2 which feeds the appropriate signals to it as demanded by the operator both by his operation of stops, as in an organ, and by his operation of the keys. Such a system will be preferred for such purposes as orchestration. The soundbox can thus be controlled by the computer to provide a simulated performance of any selected instrument or such combinations of instruments as may be provided for. In such a system moreover the programming can be such that the parts to be played by each instrument can be scored separately or played individually or in combination as may be required.

Claims (21)

1. Method of producing a visual representation of a musical work in musical notation comprising performing a rendition of said work on a keyboard, deriving from said keyboard signals representing in digital code the pitch and duration of each note of said rendition, processing said signals mathematically to mach them to a predetermined format of musical notation and producing from said signals as so processed a visual representation of the musical notation representing said work.

2. Method of producing a visual representation of a musical rendition in musical notation which comprises setting up a periodic time base to which said rendition is made substantially conformative, identifying within said time base a rhythm structure, deriving from said rendition signals in digital code indicative of the pitch, times of commencement and times of termination of individual notes of said rendition, modifying said signals to match said rhythm structure, employing the modified signals to identify the values of said individual notes in terms of said time base and generating a visual representation of said values in musical notation.

3. Method as claimed in Claim 2 in which said signals include digitally encoded representations of the times of occurrence of events being the commencements and terminations of notes of said rendition on a time scale consisting of subdivisions of the periodicity of said time base, in which said rhythm structure comprises a selected grouping of said sub-divisions to provide a pattern of time intervals within each period of said time base and in which said signals are modified by mathematical processing of their digital content to generate modified signals representing the sequence of events produced by said rendition displaced in time to conform to said rhythm structure.

4. Method as claimed in Claim 3 in which the numbers represented by said signals are rounded by said mathematical process to conform to the nearest value of said time scale identifying a boundary of a time interval within said rhythm structure.

5. Apparatus for generating a visual representation of a musical rendition in musical notation comprising a keyboard, means connected to said keyboard for deriving signals therefrom in response to a rendition on said keyboard, electronic computer means for processing said signals to provide an analysis of said rendition conformative to a predetermined time pattern representing a rhythm structure and for interpreting said analysis in terms of musical notation and display means for generating a visual representation in musical notation from the signals so processed.

6. Apparaus according to Claim 5 comprising means for sensing the state of operation of the keys of said keyboard, means for periodicaly scanning said sensing means, primary computer means for detecting changes in the states of keys of said keyboard from one scan to the next and encoding and storage means for encoding and storing information representative of the timings of said changes on a time scale related to said predetermined time pattern.

7. Apparatus according to Claim 6 comprising main computer means for deriving digitally encoded information from said encoding and storage means, mathematically adjusting said information to render it comformative to said predetermined time pattern, interpreting the events represented by the information so obtained in terms of musical notation and employing the information so interpreted to generate a visual representation of said musical notation.

8. Apparatus as claimed in Claim 7 wherein said primary computer means is arranged to compare the state of a key as detected by said sensing means with the state of the key as previously recorded in said storage means and if a change of state is revealed by such comparison to record the new state in said storage means and feed a signal signifying the changed state of said key to said main computer means.

9. Apparatus as claimed in Claim 6,7 or 8 wherein said sensing means are adapted to sense a plurality of states relative to a plurality of stages of operation of a key and signals representing successive stages are compared in said primary computer means to provide information representative of the manner of operation of the respective key.

10. Apparatus as claimed in Claim 9 including means for generating time base signals representing a time base to which a rendition on said keyboard is to be made conformative.

11. Apparatus as claimed in Claim 10 wherein the means for generating said time base signals is operable by the operator of said keyboard.

12. Apparatus as claimed in Claim 10 wherein the means for generating said time base signals are associated with said primary or said main computer means and are supplied to sound producing means to produce an audible beat to which said rendition can be matched.

13. Apparatus as claimed in Claim 10, 11 or 12 wherein said time base signals are employed to determine said predetermined time pattern.

14. Apparatus as claimed in any one of Claims 5 to 13 including sound producing means connected to generate sounds representative of the rendition on said keyboard.

15. Apparatus as claimed in Claim 9 wherein said sensing means comprises means for sensing the rest position of a key and means for sensing the operated position of a key and wherein said primary computer means is arranged to generate digitally coded information indicating the times of departure from and restoration to said rest position and said operated position.

16. Apparatus as claimed in Claim 15 wherein said primary computer means is arranged to supply interrupt signals to said main computer means only in response to a sensed movement of a key from said rest position into said operated position or vice versa.

17. Apparatus as claimed in Claim 16 wherein said interrupt signals are applied in said main computer means to trigger routines for generating visual representations of the rendition represented by the sensed key operations, said routines including mathematical rounding of the values representing in digital code the sensed times of key operation to values represented in digital code of the nearest occurring beats of said predetermined time pattern.

18. Apparatus as claimed in Claim 16 or 17 wherein said main computer means is arranged to generate a sound output in response to movement of a key from said rest position to said operated position and wherein the volume of sound generated is controlled in relation to the time interval between the sensed departure of said key from its rest position and its sensed arrival at its operated position.

19. Apparatus as claimed in any one of Claims 14 to 18 wherein said sound producing means includes sound synthesising means.

20. Apparatus for generating a visual representation in musical notation arranged and adapted to operate substantially as hereinbefore described with reference to the accompanying drawings.

21. Method of generating a visual representation in musical notation substantially as hereinbefore described.