1 The HoneyButtons Project relative keyboard was pioneered by Leon Gru- enbaum, who designed the Samchillian key- Harrison David Reiser board around this paradigm and demonstrated its advantages in improvisational performance. [7] The aim of this project is to make both F generalized and relativistic keyboards more ac- cessible and intuitive to the uninitiated as well Abstract—An electronic generalized keyboard synthesizer is as to create a general-purpose lead synthesizer proposed, using a new experimental control scheme. The con- suited to improvisation and compositional ex- trols are mediated through software and illuminated with LEDs, perimentation. As such, the project includes allowing an endlessly reconfigurable interface. a research component that will analyze the experiences of musicians who use the device in order to assess the viability of such alternate 1 INTRODUCTION control schemes. HoneyButtons is a proposed new electronic musical instrument, employing a generalized 2 DESCRIPTION keyboard layout that dynamically transposes itself with every key played. HoneyButtons de- 2.1 Interface rives its name from its hexagonal arrangement The prototype keyboard will have an array of keys, resembling a honeycomb. of 19 keys each illuminated with an arbitrary Generalized keyboards (also called isomor- color. Key color will be used to assist the player phic keyboards) arrange notes in a regular in identifying notes and other synthesizer func- grid in which adjacent notes are separated by tions. Fig. 1 shows a typical note layout, mim- regular pitch intervals along each axis. [1] Such icking a B-system chromatic button accordion, 1 keyboards are valued for their musical symme- with half steps ( 12 octave) along the upward 2 try: a chord or melody becomes abstracted into axis and whole steps ( 12 octave) going down a 2D shape or pattern that can be replicated and to the right. Time and money permitting, in any key simply by changing the starting after this inital prototype is completed, another position. [2] Chromatic button accordions have larger keyboard may be constructed or the enjoyed these advantages for over a century [3], prototype expanded to include up to 40 keys, and modern-day alternatives to the traditional the equivalent of two octaves. ”seven-plus-five” piano keyboard have become Because the interface is entirely software- available in various layouts and tunings since driven, the device is not tied to a particu- the advent of MIDI. [4][5][6] lar mapping of keys to notes. The relativistic Unique to HoneyButtons, however, is a novel control scheme described above (henceforth control scheme that maps relative note inter- called Relative Mode) is a key example: while vals to absolute key positions by centering (i.e. in Relative Mode, the device will continually transposing) the keyboard around each note center the keyboard around the last note played as it is played. Along with expanding the ef- and update the key colors appropriately, as fective range of an instrument, this ”melodic illustrated in Fig. 2. Starting with C in the cen- relativity” further abstracts the concept of a ter, pressing the key just below the rightmost melody into a sequence of intervals. Even when button will play an E note, then transpose the replicating the sequence by pressing keys in a keyboard up by one major third such that E specific order, the result may be in different is now in the center. If the same button were keys, depending on which note begins at the pressed again, the next note would be a major center. This makes certain classes of repeating third (or 5 half-steps) above E, which is A[, and melodies with complex spiralling transposi- so on. This effectively assigns a relative pitch tions (with many of J.S. Bach’s fugues as exam- value to each key, instead of the usual fixed ples) elementary to perform. The concept of the pitches. These values are represented in Fig. 3 2 A] E G −4 −1 +2 B[ G] D F B −5 −2 +1 +4 A[ D] F] C A C’ −6 −3 0 +3 +6 E[ G[ C] A] E G −4 −1 +2 +5 D[ B[ G] D F −2 +1 −4 A[ Fig. 1: bayan layout (B-system accordion) Fig. 3: relative key values for the B-system C C E E Fig. 2: demonstration of Relative Mode by number of half-steps, using the B-system as Fig. 4: Harmonic Table layout (source: http:// an example. c-thru-music.com) This separation of instrument and interface also means that the keyboard can be rearranged to suit any musical style or preference. As a advantage of spanning over two octaves on a fundamental aspect of generalized keyboards, 19-button Honeybuttons at the price of only any layout can be represented by and gener- being able to reach 8 notes of each octave at ated from two distinct note intervals, corre- a time. [5] sponding to two axes along the grid. (In the Alternative tunings are also possible: Fig. case of hexagonal grids, an interval along the 5 shows how the keys might be mapped for third axis can be found simply by adding the a scale with 19 equal divisions of the octave other two.) Countless configurations can there- (19EDO). As with the traditional B-system, the fore be created simply by adjusting the note keys to the immediate top-right and bottom- intervals in either direction. For example, the right of a given key represent the 19EDO equiv- 1 fundamental intervals of the “Harmonic Table” alents of half steps ( 19 octave) and whole steps 3 are the major third, minor third, and perfect ( 19 octave) respectively. fifth, making a wide variety of chords and Fig. 5 also shows an example of how the arpeggios rather simple. This layout, shown in colored LEDs can be used as a visual aid to the Fig. 4, is the default mapping of the commercial musician. In 12EDO—the standard followed AXiS and Opal MIDI controllers, and has the by almost all modern musical instruments— 3 Therefore, a minimal set of features has been E G B[ designated as the primary project goal, with several open-ended secondary goals to be ex- C[’ plored after the core functionality is fully tested D F A[ at each milestone. (see section 3) B] 2.2 Hardware C E[ G[ A] C]’ The prototype keyboard consists of an array of arcade-style pushbuttons mounted with high F[ D[ G] B intensity RGB LEDs. The three colors are dif- E] fused through the frosted button plastic to produce a full color spectrum, which at near- D] F] A maximum output is visible even in lighted environments. The TLC5940 chip, a specialized PWM LED driver, will be used in order to Fig. 5: a possible 19-ET mapping provide consistent power to the LEDs. Multiple chips can be daisy-chained through its serial interface to conserve pins, similar to I2C. sharps and flats share the same positions on The synthesizer module will be implemented the scale. 19EDO on the other hand has dis- in Verilog and synthesized onto a Papilio One, tinct tones for most of its sharps and flats, the an open-hardware FPGA development board equivalent of adding 7 black keys per octave on centered around the Spartan-3E. Code for this a piano. Therefore, to avoid confusion, sharps synthesizer is based on a previous digital de- are identified with “warmer” (red) colors and sign project involving five other ECE 5710 flats with “cooler” (blue) colors as a sort of students. [8] Its feature set is currently being synaesthetic mnemonic. Similar uses of color, expanded to include portamento (i.e. sliding such as applying a gradient along the full tonal pitch) and wavetable synthesis, which would range of the instrument, can help the performer enable a rudimentary form of custom synth distinguish octaves and absolute pitch. voices by supplying recorded or artificial wave- Since HoneyButtons is intended to be a form samples. Due to the restrictions of Rela- largely standalone MIDI device, the LEDs and tive Mode, polyphony will not be supported, buttons will also be used to identify and control but additional features such as digital filters all other functions, e.g. to change the MIDI and effects are open to possible future devel- channel and voice and switch between various opment. keyboard layouts. Additionally, an interactive The Papilio platform includes an Arduino- tutorial mode for teaching and practicing the compatible soft core based on the AVR8 pro- use of the keyboard (with or without Relative cessor and supports a variety of peripheral Mode) will ideally be available before the start modules known as “wings”. To interface with of user trials, but is still in the speculation other audio equipment, the Papilio One will be phase. An external pedal will be used to access augmented with a MIDI Audio Wing, which 1 these features, either as a modifier key for provides a MIDI port and ⁄8” stereo audio jack. chorded commands or as a “home” key that The MIDI port will allow HoneyButtons to act accesses a central menu. as a MIDI controller for external devices, while Discovering intuitive interfaces for these ex- the built-in low-pass filter allows analog audio tra features may require much iteration and output from a digital source by first using the testing; in fact, because of the experimental FPGA to perform Delta-Sigma encoding, i.e. and highly reconfigurable nature of the device, converting digital audio samples into a high- a nearly unlimited amount of time could be speed 1-bit waveform. (See [9] for an example.) spent simply developing and testing the UI. For the sake of testing the prototype, however, 4 TABLE 1: Estimated power usage User RGB LEDs 20 × 168 mW = 3.36 W TLC5940 4 × 1.0 W = 4.00 W Keyboard HC4052 3 × 500 mW = 1.50 W Papilio One 1 × 115 mW = 0.12 W 8.99 W Switches LEDs n n found and likely varies with the impedance of the audio output device.