Classifications

• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H1/00—Details of electrophonic musical instruments
  • G10H1/44—Tuning means
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H1/00—Details of electrophonic musical instruments
  • G10H1/18—Selecting circuits
  • G10H1/20—Selecting circuits for transposition
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H1/00—Details of electrophonic musical instruments
  • G10H1/36—Accompaniment arrangements
  • G10H1/38—Chord
  • G10H1/383—Chord detection and/or recognition, e.g. for correction, or automatic bass generation
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H3/00—Instruments in which the tones are generated by electromechanical means
  • G10H3/12—Instruments in which the tones are generated by electromechanical means using mechanical resonant generators, e.g. strings or percussive instruments, the tones of which are picked up by electromechanical transducers, the electrical signals being further manipulated or amplified and subsequently converted to sound by a loudspeaker or equivalent instrument
  • G10H3/125—Extracting or recognising the pitch or fundamental frequency of the picked up signal
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H3/00—Instruments in which the tones are generated by electromechanical means
  • G10H3/12—Instruments in which the tones are generated by electromechanical means using mechanical resonant generators, e.g. strings or percussive instruments, the tones of which are picked up by electromechanical transducers, the electrical signals being further manipulated or amplified and subsequently converted to sound by a loudspeaker or equivalent instrument
  • G10H3/14—Instruments in which the tones are generated by electromechanical means using mechanical resonant generators, e.g. strings or percussive instruments, the tones of which are picked up by electromechanical transducers, the electrical signals being further manipulated or amplified and subsequently converted to sound by a loudspeaker or equivalent instrument using mechanically actuated vibrators with pick-up means
  • G10H3/18—Instruments in which the tones are generated by electromechanical means using mechanical resonant generators, e.g. strings or percussive instruments, the tones of which are picked up by electromechanical transducers, the electrical signals being further manipulated or amplified and subsequently converted to sound by a loudspeaker or equivalent instrument using mechanically actuated vibrators with pick-up means using a string, e.g. electric guitar
  • G10H3/186—Means for processing the signal picked up from the strings
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H2210/00—Aspects or methods of musical processing having intrinsic musical character, i.e. involving musical theory or musical parameters or relying on musical knowledge, as applied in electrophonic musical tools or instruments
  • G10H2210/325—Musical pitch modification
  • G10H2210/331—Note pitch correction, i.e. modifying a note pitch or replacing it by the closest one in a given scale
  • G10H2210/335—Chord correction, i.e. modifying one or several notes within a chord, e.g. to correct wrong fingering or to improve harmony
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H2210/00—Aspects or methods of musical processing having intrinsic musical character, i.e. involving musical theory or musical parameters or relying on musical knowledge, as applied in electrophonic musical tools or instruments
  • G10H2210/395—Special musical scales, i.e. other than the 12-interval equally tempered scale; Special input devices therefor
  • G10H2210/471—Natural or just intonation scales, i.e. based on harmonics consonance such that most adjacent pitches are related by harmonically pure ratios of small integers
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H2210/00—Aspects or methods of musical processing having intrinsic musical character, i.e. involving musical theory or musical parameters or relying on musical knowledge, as applied in electrophonic musical tools or instruments
  • G10H2210/571—Chords; Chord sequences
  • G10H2210/581—Chord inversion
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H2210/00—Aspects or methods of musical processing having intrinsic musical character, i.e. involving musical theory or musical parameters or relying on musical knowledge, as applied in electrophonic musical tools or instruments
  • G10H2210/571—Chords; Chord sequences
  • G10H2210/586—Natural chords, i.e. adjustment of individual note pitches in order to generate just intonation chords
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H2210/00—Aspects or methods of musical processing having intrinsic musical character, i.e. involving musical theory or musical parameters or relying on musical knowledge, as applied in electrophonic musical tools or instruments
  • G10H2210/571—Chords; Chord sequences
  • G10H2210/596—Chord augmented
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H2210/00—Aspects or methods of musical processing having intrinsic musical character, i.e. involving musical theory or musical parameters or relying on musical knowledge, as applied in electrophonic musical tools or instruments
  • G10H2210/571—Chords; Chord sequences
  • G10H2210/601—Chord diminished
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H2210/00—Aspects or methods of musical processing having intrinsic musical character, i.e. involving musical theory or musical parameters or relying on musical knowledge, as applied in electrophonic musical tools or instruments
  • G10H2210/571—Chords; Chord sequences
  • G10H2210/621—Chord seventh dominant
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H2210/00—Aspects or methods of musical processing having intrinsic musical character, i.e. involving musical theory or musical parameters or relying on musical knowledge, as applied in electrophonic musical tools or instruments
  • G10H2210/571—Chords; Chord sequences
  • G10H2210/626—Chord sixth
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
  • G10H2250/00—Aspects of algorithms or signal processing methods without intrinsic musical character, yet specifically adapted for or used in electrophonic musical processing
  • G10H2250/131—Mathematical functions for musical analysis, processing, synthesis or composition
  • G10H2250/161—Logarithmic functions, scaling or conversion, e.g. to reflect human auditory perception of loudness or frequency

Definitions

• This invention relates to electronic music production and reproduction and to methods for modifying electronic analogs of sound during the process of amplifying and enhancing the signals generated by a note, and in general to systems having the objective of quickly determining the fundamental frequency of a compound wave which is the sum of multiple frequencies.
• a partial or partial frequency is defined as a definitive energetic frequency band
• harmonics or harmonic frequencies are defined as partials which are generated in accordance with a phenomenon based on an integer relationship such as the division of a mechanical object, e.g., a string, or of an air column, by an integral number of nodes.
• ⁇ is a constant, typically .004.
• Examples of texts which contribute to this body of knowledge are 1) The Physics of Musical Instruments by Fletcher and Rossing, 2) Tuning, Timbre, Spectrum, Scale by Sethares, and 3) Digital Processing of Speech Signals by Rabiner and Schafer. Also included are knowledge and theory concerning various ways to measure/determine frequency, such as fixed and variable band-pass and band-stop filters, oscillators, resonators, fast Fourier transforms, etc. An overview of this body of knowledge is contained in the Encyclopedia Britannica.
• U.S. Patent 5,780,759 to Szalay describes a pitch recognition method that uses the interval between zero crossings of a signal as a measure of the period length of the signal . The magnitude of the gradient at the zero crossings is used to select the zero crossings to be evaluated.
• U.S. Patent 5,774,836 to Bartkowiak et al shows an improved vocoder system for estimating pitch in a speech wave form.
• the method first performs a correlation calculation, then generates an estimate of the fundamental frequency. It then performs error checking to disregard "erroneous" pitch estimates. In the process, it searches for higher harmonics of the estimated fundamental frequency.
• U.S. Patent 4,429,609 to Warrander shows a device and method which performs an A to D conversion, removes frequency bands outside the area of interest, and performs analysis using zero crossing time data to determine the fundamental. It delays a reference signal by successive amounts corresponding to intervals between zero crossings, and correlates the delayed signal with the reference signal to determine the fundamental .
• the present invention is a method to quickly deduce the fundamental frequency of a complex wave form or signal by using the relationships between and among the frequencies of higher harmonics. The method includes selecting at least two candidate frequencies in the signal. Next, it is determined if the candidate frequencies are a group of legitimate harmonic frequencies having a harmonic relationship. Finally, the fundamental frequency is deduced from the legitimate frequencies.
• relationships between and among detected partial frequencies are compared to comparable relationships that would prevail if all members were legitimate harmonic frequencies.
• the relationships compared include frequency ratios, differences in frequencies, ratios of those differences, and unique relationships which result from the fact that harmonic frequencies are modeled by a function of a variable which assumes only positive integer values. That integer value is known as the harmonic ranking number.
• the value of S hereafter called the sharping constant, determines the degree to which harmonics become progressively sharper as the value of n increases.
• Another method for determining legitimate harmonic frequencies and deducing a fundamental frequency includes comparing the group of candidate frequencies to a fundamental frequency and its harmonics to find an acceptable match.
• One method creates a harmonic multiplier scale on which the values of G(n) are recorded. Those values are the fundamental frequency multipliers for each value of n, i.e., for each harmonic ranking number.
• Next a like scale is created where the values of candidate partial frequencies can be recorded. After a group of candidate partial frequencies have been detected and recorded on the candidate scale, the two scales are compared, i.e., they are moved with respect to each other to locate acceptable matches of groups of candidate frequencies with groups of harmonic multipliers.
• the scales are logarithmic.
• a possible set of ranking numbers for the group of candidate frequencies is determined (or can be read off directly) from the harmonic ranking number scale.
• the implied fundamental frequency associated with the group of legitimate partial candidate frequencies can be read off directly. It is the frequency in the candidate frequency scale which corresponds to (lines up with) the "1" on the harmonic multiplier scale.
• the candidate frequencies are compared to a plurality of detected measured harmonic frequencies stemming from a plurality of fundamental frequencies.
• the detected and measured harmonic frequencies are preferably organized into an array where the columns are the harmonic ranking numbers and the rows are the harmonic frequencies organized in fundamental frequency order.
• the harmonic ranking numbers and the fundamental are known.
• the fundamental frequencies of the higher harmonics normally can be determined more quickly than the fundamental frequency, and since the calculations to deduce the fundamental frequency can be performed in a very short time, the fundamental frequencies of low bass notes can be deduced well before they can be measured.
• Figure 1 is a block diagram of a method of deducing the fundamental frequency according to the present invention.
• Figure 2 is a block diagram of a specific implementation of the method of Figure 1.
• Figure 3 illustrates a logarithmic scale whereon harmonic multipliers are displayed for Harmonics 1 through 17 and a corresponding logarithmic scale whereon the frequencies of four detected partials are displayed.
• Figure 4 is an enlargement of a selected portion of the Figure 3 scales after those scales are moved relative to each other to find a good match of three candidate frequencies with harmonic multipliers.
• Figure 5 is an enlargement of a narrow frequency band of Figure 4 showing how matching bits can be used as a measure of degree of match.
• Figure 6 is a block diagram of a system implementing the method of Figures 1-4.
• anomalous frequencies In order to deduce the fundamental frequency, f l r from higher harmonics, anomalous frequencies must be screened out and the harmonic ranking numbers of at least one legitimate harmonic group must be determined. Alternatively, the number of unoccupied harmonic positions (missing harmonics) bracketed by two legitimate harmonics must be determined.
• the general method, illustrated in Figure 1 selects candidate frequencies. Next, it determines if the candidate frequencies are legitimate harmonic frequencies having the same underlying fundamental frequency. Finally, the fundamental frequency is deduced from the legitimate frequencies.
• f H , f M , f L The candidate frequencies of a trio of partials, organized in descending frequency order.
• R H , R M , R L The ranking numbers associated with f H ,
• F L The lowest fundamental frequency, f ⁇ , which can be produced by the source of the signal .
• F H The highest fundamental frequency, f l f which can be produced by the source of the signal .
• the method uses relationships between and among higher harmonics, the conditions which limit choices, the relationships the higher harmonics have with the fundamental, and the range of possible fundamental frequencies. Examples are:
• Ratios of detected candidate frequencies must be approximately equal to ratios obtained by substituting their ranking numbers in the model of harmonics , i.e.,
• the candidate frequency partials f H , f M , f L which are candidate harmonics, must be in the range of frequencies which can be produced by the source or the instrument .
• the harmonic ranking numbers R H , R M , R L must not imply a fundamental frequency which is below F L or above F H , the range of fundamental frequencies which can be produced by the source or instrument .
• the integer R M in the integer ratio R H / R M must be the same as the integer R M in the integer ratio R M / R L , for example. This relationship is used to join Ranking Number pairs ⁇ R H , R M ⁇ and ⁇ R M , R L ⁇ into possible trios ⁇ R H , R M , R L ⁇ .
• the methods analyze a group of partials or candidate frequencies and ascertain whether or not they include anomalous frequencies.
• each group analyzed will contain three partials. If the presence of one or more anomalous frequencies is not determined, the group is considered to be a group of legitimate harmonic frequencies.
• the ranking number of each harmonic frequency is determined, and the fundamental frequency is deduced. When the presence of one or more anomalous frequencies is determined, a new partial or candidate frequency is detected, measured and selected and anomalous frequencies are isolated and screened out. This process continues until a group of legitimate harmonics frequencies remain. In the process, the ranking numbers of legitimate harmonic frequencies are determined and verified.
• the fundamental frequency is then computed by a variety of methods. Adjustments are made considering the degree to which harmonics vary from
• the following is an example of a method implementing the compact flow chart of the method of Figure 1 to deduce the fundamental frequency and is illustrated in Figure 2.
• the method tests a trio of detected candidate partial frequencies to determine whether its members consist only of legitimate harmonic frequencies of the same fundamental frequency. When that is not true, additional candidate frequencies are inducted and substituted for ones in the trio at hand until a trio of legitimate harmonics has been found. When such a trio is found, the ranking numbers associated with each member are determined and the fundamental frequency is deduced.
• the method as described herein illustrates the kinds of logical operations that will be accomplished either directly or indirectly. The actual implementation will incorporate shortcuts, eliminate redundancies, etc., and may differ in other ways from the implementation described below.
• K x is the highest harmonic ranking number which will be assigned/considered.
• the value of K ⁇ is set by comparing the expected % error in the measurement of the frequency of the K x th harmonic with the value of the quotient of the integer ratio [(K- + 1) ⁇ K ⁇ [K- ⁇ (K x - 1)]
• a default value for K x will be set equal to 17 and will be revised to conform to knowledge of the instrument at hand and the expected error in frequency measurements .
• K 2 is the maximum expected number of missing harmonics between two adjacent detected harmonic frequencies.
• the default value of K 2 is set equal to 8.
• K 3 is equal to the expected maximum sum of the missing harmonics between two harmonics containing one intervening or intermediate harmonic, plus 1.
• the default value for K 3 is set equal to 12.
• Step 1 Set constants/parameters for the instrument or signal source.
• F H 300 Hz
• F L 30 Hz
• F mx 2,100
• Step 2 Detect, measure and select the frequencies of three partials, for example.
• the frequencies are detected and measured in the order in which they occur.
• Three frequencies or partials, having an energy level significantly above the ambient noise level for example, are selected as candidates of possible legitimate harmonics.
• Higher frequencies, and consequently higher order harmonic frequencies, naturally are detected and measured first.
• the following example assumes an exception where a lower harmonic is detected before a higher one, and illustrates how that exception would be processed.
• 1 st frequency measured 722 Hz
• 2 nd frequency measured 849 Hz
• 3 rd frequency measured 650 Hz.
• Step 3 The three candidate frequencies are arranged in order of frequency and labeled f H , f M , f L -
• Step 4 Possible trios of ranking numbers are determined for the candidate frequencies f H , f M , f L .
• the quotients of the ratios f H /f M and f M /f L are compared to the quotients of integer ratios I a /I b , where I a and I b are both ⁇ K x , a given threshold.
• K 2 is set equal to 17 for illustrative purposes.
• the ratios may also be f H /f L an ⁇ M /f or £H/ £M anc ⁇ H /f or an Y ° tne inverses.
• Step 5 All possible trios of ranking numbers are eliminated which imply a fundamental frequency f x outside the range defined by F L and F H .
• Step 7 The quotient of the difference ratio D H,M / D M#L i s compared to the quotients of small integer ratios I c /I d where I c ⁇ K 2 , and I c + I d ⁇ K 3 .
• a cursory review of field data confirms these assumptions. If the other difference ratios are used, the values of K 2 and K 3 are appropriately set using the same analysis.
• Step 8 Any difference ratio which implies a fundamental frequency f r ⁇ F L is disqualified.
• Step 9 Any trio of ranking numbers R H , R M , R L is disqualified if the integer ratio I c /I d which matches the frequency difference ratio is inconsistent with the corresponding ranking number ratios
• Step 10 If there are unresolvable inconsistencies, go to Step 11.
• Steps 12-14 To find a trio of candidate frequencies, the original three candidate frequencies are used with one or more additional candidate frequencies to determine a legitimate trio. If it is the first time through the process for a trio, proceed to Step 13 to select a fourth candidate frequency and on to Step 14 to replace one of the frequencies in the trio. The determination of a legitimate trio consisting of the fourth candidate frequency and two of the original trio of candidate frequencies is conducted beginning at Step 3.
• Step 12 proceeds directly to Step 14.
• a second original candidate frequency is replaced by the fourth candidate to form a new trio. If this does not produce a legitimate trio, the fourth candidate will be substituted for a third original candidate frequency. If no legitimate or consistent trio has been found after substituting the fourth candidate frequency for each of the frequencies in the original trio, which is determined as the third pass through by Step 12, go to Step 15.
• the value 849 is replaced by 602 to form the trio ⁇ 722, 650, 602 ⁇ which is designated as new candidate trio ⁇ f H , f M , f L ⁇ .
• Step 15 A fifth and sixth candidate frequencies are selected.
• the fourth frequency is combined with the fifth and sixth candidate frequencies to form a new beginning trio and the method will be executed starting with Step 3.
• Step 12 will be reset to zero pass throughs .
• Step 16 If after all frequencies detected and measured have been selected and determined by Step 11 and no consistent or legitimate trio has been found at Steps 7-10, the lowest of all the frequencies selected will be considered the fundamental .
• Step 17 Deduce the fundamental frequency by any one of the following methods for example wherein
• the deduced fundamental could be set equal to any of a variety of weighted averages of the six computed values . For example :
• Step 9 If after Step 9 is completed, two or more consistent sets of ranking numbers remain, the fundamental f x should be recalculated with each set of ranking numbers and the lowest frequency obtained which is consistent with conditions described in Steps 3 through 9 is selected as the deduced fundamental frequency f x .
• S the ratio of the frequency differences (f H -f M ) ⁇ (f M -f L ) will be approximately equal to a small integer ratio and
• trios of legitimate harmonic partials are isolated and their corresponding ranking numbers are determined by a) Comparing the quotients of f H ⁇ f M and f M ⁇ f L to the quotients of ratios G(R H ) ⁇ G(R M ) and
• HM Scale Harmonic Multiplier Scale
• Each successive mark on the scale represents the previous multiplier number itself multiplied by [2 x S] 1/1200 Assume that a string of bits is used each representing one cent. The n th bit will represent the multiplier [(2 x S) 1/1200 ] (n - 1 ⁇ . Selected bits along the HM Scale will represent harmonic multipliers and will be tagged with the appropriate harmonic number: f j will be represented by bit 1, f 2 by bit 1200, f 3 by bit 1902, f 4 by bit 2400,..., f 17 by bit 4905. This scale is depicted in Figure 3.
• the starting gradient marker represented by bit 1
• F L the frequency of the starting gradient marker
• F L x[(2x s) 1 ' 1200 ] 1 the next by F L x [ (2 x S) 1/1200 ] 2 .
• the n th bit will represent F L x [ (2 x S) 1/1200 ] "- 1 .
• This scale is known as the Candidate Partial Frequency Scale and is hereafter called the CPF Scale. It is depicted along with the HM Scale in Figure 3.
• Figure 4 shows the portion of the scales in which the detected candidate frequencies lie after the scales have been shifted to reveal a good alignment of three frequencies, i.e., the 4 th frequency detected, 421 Hz, combined with the 1st and 3 rd frequencies detected, 624 Hz and 467 Hz.
• One method for measuring the degree of alignment between a candidate partial and a harmonic multiplier is to expand the bits that mark candidate partial frequencies and harmonic multipliers into sets of multiple adjacent bits.
• 7 bits are turned on either side of each bit which marks a harmonic multiplier.
• 7 bits are turned on either side of each bit marking a candidate partial frequency.
• the number of matching bits provides a measure of the degree of alignment.
• the number of matching bits in a trio of candidate frequencies exceed a threshold, e.g., 37 out of 45 bits, then the alignment of candidate partials is considered to be acceptable and the candidate frequencies are designated as a trio of legitimate harmonic frequencies.
• Figure 5 illustrates the degree of match, e.g., 12 out of a possible 15, between one candidate partial frequency, i.e., 624 Hz, and the multiplier for the 12 th harmonic.
• the implied ranking numbers are used to test for unresolvable inconsistencies using the logical Steps 6 through 9 of Method 1. If no unresolvable inconsistencies are found and the implied fundamental is lower then F L or higher than F H , then the scales are moved in search of alignments implying a higher fundamental or a lower fundamental respectively. When no unresolvable inconsistencies are found and the implied fundamental lies between F L and F H , then the implied fundamental f 1 becomes the deduced fundamental .
• Another method of deducing the fundamental frequency entails the detection and measurement or calculation of harmonic frequencies for a plurality of fundamental frequencies.
• the frequencies are organized in an array with fundamental frequencies being the rows and harmonic ranking numbers being the columns.
• the frequencies of the higher harmonics, as they are detected are compared row by row to the harmonic frequencies displayed in the array.
• a good match with three or more frequencies in the array or with frequencies interpolated from members of the array indicate a possible set of ranking numbers and a possible deduced fundamental frequency.
• the deduced fundamental frequency is set equal to the lowest of the implied fundamental frequencies that is consistent with the notes that can be produced by the instrument at hand.
• the array is an example of only one method of organizing the frequencies for quick access and other methods may be used.
• Methods I, II and III above can be used to isolate and edit anomalous partials. For example, given a monophonic track of music, after all partials have been detected during a period of time when the deduced fundamental remains constant, these methods could be used to identify all partials which are not legitimate members of the set of harmonics generated by the given fundamental . That information could be used, for example, for a) editing extraneous sounds from the track of music; or b) for analyzing the anomalies to determine their source .
• S is a sharping constant, typically set between 1 and 1.003 and n is a positive integer 1, 2, 3,..., T, where T is typically equal to 17. With this function, the value of S determines the extent of that sharping.
• a system which implements the method is shown in Figure 6.
• a preprocessing stage receives or picks up the signal from the source. It may include a pickup for a string on a musical instrument.
• the preprocessing also conditions the signal . This may include normalizing the amplitude of the input signal, and frequency and/or frequency band limiting.
• a frequency detection stage isolates frequency bands with enough energy to be significantly above ambient noise and of appropriate definition.
• the fast find fundamental stage performs the analysis of the candidate frequencies and deduces the fundamental .
• the post processing stage uses information generated by the fast find fundamental stage to process the input signal. This could include amplification, modification and other signal manipulation processing.
• the present method has described using the relationship between harmonic frequencies to deduce the fundamental .
• the determination of harmonic relationship and their rank alone without deducing the fundamental also is of value.
• the fundamental frequency may not be present in the waveform.
• the higher harmonics may be used to find other harmonics without deducing the fundamental.
• post processing will use the identified harmonics present .

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• Electrophonic Musical Instruments (AREA)
• Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
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• 1999
  • 1999-10-02 ID IDW20010875A patent/ID29029A/id unknown
  • 1999-10-29 DE DE69904640T patent/DE69904640T2/de not_active Expired - Lifetime
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  • 1999-10-29 DK DK99956737T patent/DK1125272T3/da active
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• 2000
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• 2002
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• 2011
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