GB2449459A - Damping means for strings of an Autoharp / Zither - Google Patents

Abstract

An Autoharp or fretless zither has a plurality of strings t thereon that may be plucked or strummed. A series of damper bars w having pads thereon are normally in contact with said strings and are biased via springs (q fig 4). A series of piano like keys e are provided on said autoharp and act over one octave. Depressing a selected key causes a pulley string to lift said damper from said string and thus allows the string to resonate when plucked. Said damper said pads may be felt or foam. Said pulley cords may be made from waxed linen.

Description

Description

Background Discussion

Fretless Zithers, and Related Instruments A fretless zither is a harp type instrument (many strings). The body is usually quite flat when compared to a guitar, and smaller in size. It is usually strung with steel strings of varying gauges and lengths to produce different pitches. Fretless zithers are designed to be played either with the instrument sithng on a flat surface, or held on the lap. All harps and zithers have problems as playing interfaces for musicians. Because of this, tinkering with the interface is an integral part of the history.

Examples of fretless zithers are most commonly strung in a linear fashion, with longer and thicker gauge (usually steel wound) bass strings at the left, and shorter thinner gauge strings to the right. As the instrument is designed to be portable, it is quite small and therefore the strings are quite close together. Playing melodically on such an instrument is difficult, even with a simple diatonic tuning, when compared to a keyboard type interface or a fretboard, such as is found on a guitar. Harmonic playing is also difficult with a linear stringing. Individual string combinations must be plucked together to form chords. To easily play in this way the instrument must be much bigger, like a harp, with wider spacing between the strings. The upright position, and wider string spacing of a harp enable chord combinations to be picked accurately. Even so, smaller folk harps are commonly tuned diatonically, or in an extended diatonic tuning. The concert harp deploys a moveable bridge, such that by means of a pedal each string can be crooked to three different tunings. Thus it is a fully chromatic instrument, but essentially diatonic in its immediate playing interface. Because of this, once again, the instrument lacks versatility in some ways.

There are examples of various stringing configurations throughout zither history. The concert zither, for example integrates a fretboard section for melodic playing, with wide spacing on these strings, and strings groups of different gauge strings designed for chord work across the main body of instrument; these are closely strung as they do not need to be individually picked out. The unusual string groupings enable the instrument to be picked and strummed in combination. This is a versatile instrument, but is notoriously difficult to master. It also requires constant retuning of the chord groupings in order to achieve its full potential.

Another approach is to hammer the strings individually, by hand. This is the approach used by dulcimer and cymbalon type instruments. This produces good accuracy for melodic playing, but limits the available polyphony.

Autoharps The most common damping mechanism is deployed in all autoharp type instruments.

This is spring mounted chord bar across a zither strung in a linear fashion. Simpler models are diatonic, or slightly extended diatonic, designed to play in two or three keys.

Chord bars are placed on springs above the strings. When the chord bar is pressed and held in contact with the strings, felts spaced along the length of the damper bar, damp strings extraneous to the desired chord, thus the only strings that are allowed to resonate are the members of the chord. The damping mechanism means that this instrument can be rhythmically strummed as well as plucked. A smooth change of chord is accomplished by allowing the first chord bar to rise, whilst pressing the next chord bar against the strings.

The autoharp has always been a popular instrument. It is easy to learn, but is severely limited in many respects. Since the technology of the Reaph damping action is designed to replace the autoharp chord bar damping action, the limitations of the original system are now discussed in detail.

Perhaps the most disappointing aspect of the autoharp action is that it remains a very limited instrument even in the area of its supposed main strength, rhythmic harmonic playing, designed for accompaniment. The reason for this is obvious, a 12 bar autoharp will cover the most significant tnads in three different keys, it will also provide some dominant sevenths. This limits the instrument very strictly to certain genres of music. It is good for simple song based material, or some forms of folk. There are a significant number of attempts to extend the chord range of this instrument. Commonly 21 or 24 bar chromatic autoharps are available. This certainly extends themodulatory capacity of the instrument. Yet the range of chord available remains strictly limited. Generally chords are triadic in nature, and these are by no means complete. The instrument remains incapable of supporting modal thinking -integral to many Western folk music traditions. It is also incapable of easily integrating into Jazz traditions, and totally incapable of integrating into Western classical traditions. It is true that many attempts have been made to extend the chord range of the instrument, in order to accomplish this. All of these take the approach of further complicating the chord bar systems, including complex combinations of chord bars. All of these systems are possible to learn, but the interlace presented to a musician becomes very complicated indeed and quite difficult to play. This goes against the original ethos of the instrument.

Furthermore, the interface remains musically un-intuitive. Learning a guitar or a piano necessarily requires that the player acquire some music theory skills -whichever genre of music is attempted. Generally speaking, intuitive grasp of functional harmony and melodic structure improve as the player improves. This is true at both an intellectual, and instinctive level. This is not however, true of the autoharp where the actual playing of the instrument remains quite disconnected from aspects of reading or understanding of what is being played. The equivalent activity is to continuously redesign the interlace -changing around chord bar arrangements and designing specific chord bars for different musical situations. This develops a cerebral sense of music theory, but not an instinctive sense of theory in practice. It also renders the instrument difficult to bring to ensemble situations. An instrument that needs to be continuously rebuilt in order for the musician to contribute effectively is by no means ideal.

If the instrument remains harmonically basic, then melodically it is even more unsatisfactory. Here a method for achieving clean melody playing is described. 1 (Beginning with the editor's note) "As you know the autoharp is based entirely on chords and all melody notes are derived by using different chords for each note. In contrast a piano allows one to play a continuous chord with one hand while playing a melody "over" that chord with the other hand. Up until now, it hasn't been possible to achieve the same effect on the autoharp -that is, not until Carey Dubbert and his special bars.

The Autpharp Owner's Manual p.66. Ed Orthey. (article by Carey Dubbed) Pub. Mel Bay 2000 (Dubbert) The two special chord bars explained here provide a compromise between changing chords whenever needed to provide a given melody note and using open chording so as not to have to change the chord to provide a given melody note. With the first method, the chord structure of the piece is altered, and the chords usually progress much faster than would be called for by the piece. This can tend to sound choppy and fatigue the ear. The second method allows keeping the chord progression that may be called for by the piece and still have the ability to play melody notes outside the current chord.

The two special bars are best placed at the top and bottom of the harp where the thumb... and little finger can most easily press the bars.

The following illustration is my D autoharp. ... The special bars target one specific key and work as a pair in that key. My thumb presses the number I bar, and my little finger presses the number 2 bar. In the adjacent keys [subdominant and dominantj, one of the special bars will be applicable and the other occasionally. The bars are cut such that one bar accounts for every other note in the key selected, and the other bar allows for the other (also every other) notes in the selected key. Pressed at the same time, all the notes would be damped in the upper couple of octaves.

The bottom octave has all the felt cut out on bars, allowing the bass strings to vibrate and sustain. ... A chord is strummed or picked with a standard chord bar which includes notes in the lower octave of the harp (although other notes may well be sustained). Then, after letting up on the original bar, melody notes can be picked cleanly going back and forth on the two special bars without altering the basic sustaining chord." All of this is to achieve the correct damping to play a simple melody. The instrumental interlace is effectively compared in the quoted editor's note to the ease with which this is accomplished on a piano.

All of this illustrates that whilst both advanced harmonic and melodic playing can be accomplished on this instrument, the interface for advanced players remains highly esoteric, and ungainly in practice. One effect of this is that skills developed in learning the autoharp are not readily transferable to other musical instruments, and conversely, the instrument is unattractive to accomplished musicians generally, as its limitations are immediately apparent. In general the instrument has never made an impact in the mainstream of Western musicianship, and its evolution is rather isolated and specialized.

Conceptualising the Reverse Action Piano Harp (Reaph) The development I propose is to replace the autoharp sprung chord bar action, with a reversed action damper bar arrangement that is controlled through a pulley system from one octave of a full sized piano keyboard. The integration of a keyboard with this instrument is not in itself a new idea. I have been able to identify several historical examples of instruments which attempt this2. All of them are fundamentally different from the Reaph in conception and construction. The keys on these instruments have 2 www.freflesszithers.com: for example The Celestophone, patent 1912, The Marxophone, The Supertone Phonoharp, The Piano Mandolette, Menze's Piano Zither, patent 1898, The Dolceola.

nothing to do with the action of the damper bars. Instead, each piano key operates a hammer of some sort. The conception is, as with other keyboard instruments -one key depressed will sound one string on the instrument.

Similarly, a reverse action is not in itself a new idea, a similar system is integral part of piano design. I have not been able to find a single example of a fretless zither conceived in this way during its evolution, however.

The term reverse action refers to the fact that the dampers are in contact with the strings when the instrument is at rest, as opposed to the over-sprung action of an autoharp. This is a fundamentally different conception of the instrument. In the autoharp at rest, all of the damper bars are raised by the springs, above the instrument.

Conversely the Reaph at rest places all of the damper bars in contact with the strings.

The damper felts do not damp chords. Instead each damper bar aligns the felts with each octave occurrence of a single pitch. Each damper is then attached to the corresponding keyboard key through means of a pulley system. The original autoharp springs are utilized, but reversed -keeping the damper bar in continuous contact with the strings, until a key is depressed. Thus pressing a piano key does not in itself make a sound. The key is not attached to a hammer system, it simply raises the damper bar, enabling the strings to be strummed or plucked. Thus, even though the instrument is differently conceived, the effect is that the interface has some similarities to the original autoharp interlace. In order to play a D pitch -the D key is depressed, raising the D damper from all octave occurrences of the D strings. Strumming the instrument across its range then sounds all of the D pitches. More accurate strumming or plucking sounds individual pitches, yet the damping of the surrounding pitches is maintained. Lifting the finger from the key damps the D at once, and the instrument returns to silence, as lifting the finger on a piano returns the instrument to silence.

As a playing interlace, this renders the instrument far more intuitive to a trained musician, and also more versatile. It induces an intuitive connection between the activities of the left hand -playing the keyboard, and the right hand -strumming/plucking the instrument. Let us consider the change produced from the points of view of harmonic and melodic playing.

Harmonic playing is greatly enhanced by this system. In fact it is possible to play any chord, and to change simply between them as on a keyboard. Chord change is more fluid, because common notes can be held down over the change. Moreover individual notes can be added and subtracted to a chord during rhythm playing producing far more subtle shading. Suspensions are easy to create, and the resolutions are fluid. The instrument is capable of playing supporting rhythmic harmony, found in all folk traditions easily. Additionally, and importantly for these traditions, it is possible to take a modal approach to accompaniment, generating drone notes, and secundal and quartal chords.

Fluid pentatonic or whole tone scales can be generated. This instrument is also capable of performing a rhythmic/harmonic function within a jazz ensemble. A good knowledge of four and five note substitutions and their inversions on a keyboard is immediately transferable to a versatile strumming/picking environment; this is limited only by the knowledge and skill of the player. Thus 9ths, liths and l3ths are easily created. 5ths can be raised or flattened -the full chromatic array is available.

Melodically the instrument is also considerably enhanced. The ability to produce a single line of melody develops intuitively with practice. Depressing one key with the left hand enables the right hand to strum every octave occurrence of the desired pitch.

Strumming becomes isolated to single pitches through practice, and this process is highly intuitive in development.

One difficulty with melodic playing is that because the keyboard is only one octave, the left hand must continuously transpose the melody to remain within this range. In practice I have found that an ability to accomplish this at sight develops quite quickly.

However a simple notation system can help a less skilled musician to overcome this.

Two staffs of Western notation are presented to the musician to read at sight. The top line notates the melody; the lower line, which can be in bass or treble clef, renders the pitches of the melody to a single octave. This mimics piano notation rather precisely, and is easy for a pianist/keyboard player to read.

Combinations of melodic and harmonic playing can be accomplished. A skilled improviser at the piano can very quickly transfer to this instrument.

Melodically, the instrument still has limitations when compared to a guitar, or any continuous tone instrument. It is difficult to produce ornamentation -turns and frills are not easy. However, neither are these easy on a harp. All musical instruments are a compromise in one way or another.

Technical Description

Piano keyboard mechanism One octave of full size piano keys is fixed in the position illustrated in figures 1 and 2.

This playing position is carefully considered. Firstly comfortable access must be provided for the left hand to depress the keys, whilst the right hand is able to strum and pluck the strings. It is for this reason that the keyboard housing raises the keyboard 10.3 cm from the strings: this enables the right hand to move freely underneath the left hand. The piano keyboard is also placed slightly overhanging the top rail -on the right hand side of the instrument. The lever action overhangs the dead pin block by approximately 9 cm, thus lengthening the instrument by this amount. Again, this allows comfortable access for the strumming hand. The instrument is played on its side, the strum position more resembling a guitar than the traditional upright position of an autoharp.

From a mechanical point of view the placement of the left side of the keyboard housing slightly to the left of centre of the instrument, enables a series of eyes (described below within the pulley system) to be attached directly to the inside lower left side of the keyboard housing, such that they are centred, and in line with the final set of damper bar pulley-wheels. The entire pulley system is covered by the keyboard housing.

The prototype has utilized one octave of a keyboard, cannibalised from a four octave MlDl keyboard. Each key in the octave is attached to a wooden rod: the wooden key rods extend beyond the axis point Depressed keys therefore produce a lever action.

The ends of the pulley strings are attached to the ends of each of the wooden key rods by means of pegs. Piano key travel is restricted to 13mm by a wooden block placed across the front of the keyboard housing, covered in craft foam.

Key Crooks (For Diatonic, and Extended Diatonic instruments Only) Diatonic, and extended diatonically tuned autoharps will have fewer damper bars. An extended diatonic autoharp, such as the one used in the prototype, tunes its strings to the following pitches.

C,C#,DIE,F,F#,G,A, B. Thus, this harp will require only nine reversed damper bars, with pulley strings attached to the appropriate keys. The remaining piano keys can be crooked to the keys either side, by means of a moveable crook placed on the underside of the wooden key rod beyond the pulley string peg. This is shown in figure 6. The extended diatonic tuning allows the instrument to play in C, G and D majors. To play in A major, for example, all G strings are tuned to G#, and the G# piano key is crooked to the G piano key. The G# key will then operate the G pulley string system. As all the 0 strings have now been tuned to G# this is the pitch that will sound. This crooking system enables the maximum flexibility possible within the system, as the instrument can be tuned relatively quickly to play in any key.

Fully chromatic harps will have twelve damper bars, and will therefore not require key crooks.

Pulley mechanism The pulley mechanism is illustrated in cross section in figures 3.1 and 3.2. The two illustrations show the mechanism at rest with the damper in contact with the strings (3.1) and the key depressed, lifting the damper from the strings, acting against the force of the springs (3.2). When the key is released, the force of the springs returns the damper to its rest position in contact with the strings. It also returns the piano key to its rest position. The series of turns taken by the pulley strings allows the keyboard to be placed in a comfortable playing position with the left hand, whilst at the same time maintaining reasonable clearance for the right hand to move under the left hand and strum/pluck the entire width of the instrument just above the midpoint of the strings.

The number of pulley strings will depend on the tuning of the instrument. Fully chromatic harps will require twelve pulley strings, attached to all twelve wooden key rods. The harp used in the prototype, and drawn in the diagrams, is an extended diatonic harp. It produces nine individual pitches and therefore has nine pulley strings, attached to nine of the wooden key rods, and nine damper bars at each end. Other keys are utilized by means of the key crook system described above.

In all, each pulley string is constrained through four turns in the working prototype.

Firstly a tendency to pull the key mechanism to the left is constrained by placement of a series of pulley-wheels in line with each wooden key rod, beneath the peg hole.

Subsequently a lateral series of pulley-wheels, placed on a lateral bar across the instrument, turns the pulley strings through 90 degrees translating the upward motion of the lever into a force pulling along the length of the instrument. A further series of pulley-wheels is positioned after the back lateral bar to ensure parallel movement to the keys. The pulley strings then travel at varying angles to a series of eyes located on the inside left of the underside of the piano keyboard housing. Eyes are used at this point, rather than free running pulley-wheels for several reasons. Firstly there is very little space to add a further series of pulley-wheels on the inside of the keyboard housing, and I have not been able with my current level of skills and knowledge of materials to think of a way of miniaturizing this sufficiently. Secondly, the angle shifts are all obtuse angles (a correction rather than a full turn through 90 degrees) therefore the resulting friction caused by use of eyes rather than pulley-wheels has proved minimal. Thirdly, the angle shift of the pulley string here is not only a correction from the diagonal such that all pulley-strings now travel in a line, down the length of the instrument, it also shifts each of the pulley-strings to travel at a slight downward angle (to the final lateral set of damper bar pulley-wheels). In practice the use of eyes at this point has proved robust, and may be retained in the second prototype. The angles are shown in figures 3.1 and 3.2 and in figure 4. Figure 4 shows that the nine pulley strings enter the series of eight eyes at different points, and from different angles (twelve pulley strings and eleven eyes for a chromatic harp). Not shown is the fact that the pulley strings exit this system at corresponding intervals in the series of eyes, ensuring maximum separation between the threading of the pulley strings, as they travel in line to the final series of pulley-wheels above the damper bars, and also optimal exit angles to the damper bar pulley wheels. The damper bar pulley-wheels turns the pulley strings through an angle of just over 90 degrees downwards (towards the instrument), translating the motion along the length of the instrument into an upward force.

The end of the pulley string is attached to the middle of the damper bar. This is shown in figure 5.1. An improvement to this mechanism is also illustrated (figure 5.2), to be implemented in the second prototype. Force exerted on the middle of the damper bar only, on the first prototype, results in slightly uneven lifting at the edges of the damper bars. It is planned to attach the end of each pulley string directly to the damper bar pulley-wheel at the centre point, such that as the key is depressed, a sufficient length of pulley-string is free to unroll from the pulley-wheel. The damper bar pulley-wheel is lengthened and pulley strings similarly attached to the damper bar at two points equidistant from the midpoint of the damper bar. This will prevent one end of the damper bar lifting before the other. It will also have another benefit, allowing the entire mechanism to be disassembled more quickly and easily. It is envisaged that the diameter of the damper bar pulley wheel will have to be increased.

Pulley-wheels The pulley-wheels are made using two diameters of cylindrical metal bar, the outer running freely over the inner bar, which is lubricated. These can then be cut to very short lengths, or to a long length, such as with the back lateral bar, which provides space for twelve pulley-wheels to run over it.

Tension on the pulley strings Tension on the pulley strings must be equalized, such that each of the piano keys feels even to the player. The player is able to adjust these individually using the pegs at the ends of the wooden key rods over the dead pin block. This has proved robust on the first prototype. It is planned that hook and eye attachments, just before the damper bar pulley-wheels, will enable easier disassembly, and independent disassembly of the keyboard and damper mechanisms.

Pulley string material Waxed linen thread is used on the prototype. This material is stretch resistant, and has properties of retaining shape through the turns. It has proved a robust material through several months of use on the first prototype.

Damper bar mechanism The damper bar is reverse sprung. Two springs are placed on the damper bar, dividing the length of the damper bar into three. The springs fit flush over cylindrical metal bars mounted on the damper bar at these points. The top ends of the metal bars protrude into a drilled hole in a fixed wooden block mounted immediately above these points.

Washers are mounted on the underside of the wooden block, whose diameters are greater than the cylindrical metal bar, but less than the diameter of the springs. The distance between the top of the damper bar and the block is 1cm. This distance places the springs under partial compression. The resulting force pushes the damper bar downwards, such that at rest, all the felts on the dampers are in contact with the strings.

When a piano key is depressed the force acts against the springs, lifting the dampers 0.5cm from the strings, and compressing the springs completely. The cylindrical metal bar moves freely through the washer, protruding further up into the drilled hole, whilst the surrounding spring is compressed against the washer. The felts on the damper bar are spaced such that each occurrence of a single pitch is damped, at each octave, on a single damper bar. Therefore, for example, playing D on the piano keyboard with the left hand, lifts the damper bar 0.5 cm from the strings. The spacing of the felts enables any D string to be sounded through a strum or pluck, but all other notes will remain damped, irrespective of the accuracy of the strum. Playing 0 F# A with the left hand lifts the dampers from all octave occurrences of a D major chord. Strumming the instrument then produces a D major chord. When the piano keys are released the force of the springs simultaneously pushes the damper bars downwards, damping the strings, and returns the piano keys to the upright position. Felts

I have used the term "felts" because this is the common technical term used in autoharp manuals. In fact the material that I have used on the prototype is craft foam. I used this because it was readily available, cheap, and easy to cut accurately for purposes of continuous experimentation upon the prototype. Felt has been used on autoharps since their inception. I had confidence that foam had the right damping properties, but thought that it might quickly wear out, and that I would eventually have to replace the foam-felts on finished damper bars with approved autoharp material. In fact the foam has proved extremely robust through hours of playing, and recording the prototype instrument, and I don't see a reason to change it. I therefore include it in the patent application.

Listing of Drawings and Descriptions

Figure 1 Drawing 1/3 of actual size from above the instrument.

This shows: 1. keyboard placement and orientation.

2. Wooden key rods extending over the dead pin block.

3. Maximization of the strumming surface when compared to an autoharp.

4. Pulley system enclosed within keyboard housing.

Figure 2 Drawing 1/3 of actual size side view of the instrument.

This shows: 1. Keyboard height of 10.3cm from the strings, allowing the left hand to play the keyboard and the right hand to strum underneath.

2. Wooden key rods extending over the dead pin block.

3. Maximization of the strumming surface when compared to an autoharp.

4. Pulley system enclosed within keyboard housing.

Figure 3.1 Drawing 1/3 of actual size, cross section.

Side view of the pulley system, piano key at rest.

This shows: 1. White piano key attached to wooden key rod. A black piano key is shown as

background, to orient the observer.

2. Peg and hole system at the far end of the wooden key rod.

3. Pulley string, wound round the peg, and descending through the pulley string hole.

4. Pulley string constrained through three free running pulley-wheelsat differing orientations.

5. Pulley string passing through eye system, altering angle to damper bar pulley-wheel.

6. Damper bar pulley-wheel and damper bar at rest. Partially compressed spring (not shown) maintains contact with the string.

Figure 3.2 Drawing 1/3 of actual size, cross section.

Side view of the pulley system, piano key depressed.

This shows: 1. White piano key attached to wooden key rod (depressed). A black piano key is

shown as background, to orient the observer.

2. Peg and hole system at the far end of the wooden key rod.

3. Pulley string, wound round the peg, and descending through the pulley string hole.

4. Pulley string constrained through three free running pulley-wheels at differing orientations. I0

5. Pulley string passing through eye system, altenng angle to damper bar pulley-wheel.

6. Damper bar pulley-wheel and damper bar raised from the string. Spring (not shown) is at full compression.

Figure 4 Drawing 1/3 of actual size, cross section Pulley system from above. This shows the angles corrected by the series of eyes, such that pulley strings travel in line to the damper bar pulley-wheel.

Figure 5.1 Drawing 1/2 of actual size showing damper bar spring mechanism and damper bar pulley-wheel and pulley string.

Figure 5.2 Drawing 1/2 of actual size showing damper bar spring mechanism and proposed damper bar pulley-wheel improvement. This should prevent uneven lifting at the ends of the damper bar, caused by lifting from the centre point only, It is envisaged that the diameter of the pulley-wheel will have to be increased.

Figure 6 Actual size drawing, showing the key crooking mechanism, allowing one piano key to be crooked to either of the adjacent keys. (Diatonic and extended diatonic harps only).

Key to Drawings (a) Toe pin block (b) Dead pin block (C) Bass rail (d) Top rail (e) Keyboard (f) Wooden key rod (9) Damper bar (h) Spring mounting (i) Peg U) Pulley string (k) Keyboard housing (I) Back lateral bar (pulley-wheel) (m) Damper bar pulley-wheel (n) Pulley-wheel (0) Eye (p) Pivot point (q) Spring (r) Washer (s) Damper bar felt (t) string (u) Key crook (v) Key depressed (w) Damper bar raised

Claims (11)

1. Claims 1. Integrating one octave of full sized piano keys to replace an

   autoharp spring-mounted action.
2. 2. Positioning of the piano keyboard, to provide comfortable playing access for right hand, strumminglplucking the strings of the instrument underneath the left hand, playing the piano keyboard.
3. 3. Connection of the piano keys, as levers, to a pulley string system connected to reverse sprung damper bars.
4. 4. Pulley string system, using waxed linen thread for pulley string, and two gauges of cylindrical metal bar for pulley wheels, placed within the keyboard housing.
5. 5. Key crook system, allowing diatonic, and extended diatonic harps to be tuned to different keys and modes efficiently.
6. 6. Reverse sprung damper bars, such that at rest, force from the springs (partially compressed) places the damper bars in continuous contact with the strings, as opposed to the action of an autoharp, whose damper bars are mounted on springs placed above the strings.
7. 7. Reverse sprung damper bars, such that when a piano key (lever) is depressed, springs at full compression raise the damper bar 0.5cm from the strings
8. 8. Reverse sprung damper bars, such that when a piano key (lever) is released, force from the springs (at full compression) returns the damper bar in contact with the strings, silencing the strings, and simultaneously returns the piano key to the upright position.
9. 9. Arrangement of the damping felts, spaced along the damper bar, to continuously damp each octave occurrence of a single pitch until released through depressing a key, as opposed to felts spaced to produce chords on a spring mounted damper bar.
10. 10. Use of craft foam, rather than felt as a damping material:
11. II.The acronym REAPH, from REverse Action Piano Harp -Pronounced ree-af.