The Hyasynth
The Hyasynth is a novel synthesiser I have designed over the last few years. It is a free pitch instrument designed to provoke new approaches to intonation. It is named for Giacinto Scelsi, whose name means Hyacinth in Italian, and whose experiments with the ondiola opened new avenues of microtonal experimentation.
Its development was intended to allow players and composer without proficiency in free pitch instruments to swiftly model and execute new harmonic relationships. In so doing, I created a surprisingly intuitive and embodied performance medium that has altered my relationship to pitch production.
Its development was intended to allow players and composer without proficiency in free pitch instruments to swiftly model and execute new harmonic relationships. In so doing, I created a surprisingly intuitive and embodied performance medium that has altered my relationship to pitch production.
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The synthesiser is currently in its second prototype. At this stage, it is an Arduino-based controller communicating with a Max patch via serial port. The synthesiser consists of three key pitch functions: the rotary encoder pitch wheels, the combination tone keypad, and the mutual control functions. Each of these allows for a different type of interaction with pitch.
This instrument was developed alongside a consideration of the pitch continuum that views proportion and symmetry as mutual antagonists. The topic of future TEMPO article, this framework posits new connections between equal temperaments and Just Intonation that suggest productive harmonic interactions between the two. |
The Pitch Wheels
Pitch as continuum.
At the heart of the synthesiser are four high-resolution rotary encoders. These are mapped to the pitch of four synthesiser voices, allowing the performer to accurately select notes within one cent of accuracy. This is a free-pitch approach, as described by Patrizio Barbieri, meaning that the performer must continuously tune notes as they perform, as they might on a stringed instrument or a theremin. They give the electronic perform intuitive access to pitch as a glissando continuum and the ability to use the beating of pitch relationships to tune.
By default, a 360° rotation of the encoder is mapped to an octave of pitch space, but this is editable: any ratio may be selected as ‘the period’. This allows for varied geometric relationships to the pitch circle. For example, half- and quarter-circle rotations are easily visually found, but these two- and fourfold divisions of the period produce very different sonority depending on the size of the period. For a 2:1 octave, the four quarters of the circle produce a diminished seventh chord, for a 3:2 fifth, they produce a scale of 175¢ steps.
By default, a 360° rotation of the encoder is mapped to an octave of pitch space, but this is editable: any ratio may be selected as ‘the period’. This allows for varied geometric relationships to the pitch circle. For example, half- and quarter-circle rotations are easily visually found, but these two- and fourfold divisions of the period produce very different sonority depending on the size of the period. For a 2:1 octave, the four quarters of the circle produce a diminished seventh chord, for a 3:2 fifth, they produce a scale of 175¢ steps.
The amplitude of the voices is controlled by a potentiometer. They are triggered by pressing a button or by MIDI. This button may be set to either latching or momentary. The position of the wheel is shown by a ring of LEDs; the pitch ‘jumps’ when a new period size is selected.
The Combination Tone Keypad
Pitch as proportion.

These four voices are accompanied by twelve more. These twelve voices are the sum and difference tones of the first four voices. Their pitch, then, cannot be directly controlled, but is altered by any interaction with the pitch wheels. All sixteen voices (the four pitch wheels and the twelve combination tones) can be triggered with MIDI, allowing for arpeggiation and sequencing.
The presence of these combination tones allows for the intuitive tuning of the pitch wheels to Just Intervals. To simplify: when a pitch is in tune with its combination tones, it is tune to a simple Just ratio. The combination tones reveal the proportional relationships latent in the chosen pitches, projecting their spectrum in ways that can be intellectually unexpected but that are aurally resonant. This approach is informed by Marc Sabat’s theory of tunability, which uses difference tones as a fundamental way of considering consonance and dissonance.
The amplitude of the voices is controlled by four potentiometers, each of which is associated with a pitch wheel. The combination tone’s amplitude is the product of the amplitude of the potentiometer of the two pitch wheels with which it is associated. They are triggered by pressing a button, laid out in a simple matrix, or by MIDI. Their buttons may be set to either latching or momentary.
The presence of these combination tones allows for the intuitive tuning of the pitch wheels to Just Intervals. To simplify: when a pitch is in tune with its combination tones, it is tune to a simple Just ratio. The combination tones reveal the proportional relationships latent in the chosen pitches, projecting their spectrum in ways that can be intellectually unexpected but that are aurally resonant. This approach is informed by Marc Sabat’s theory of tunability, which uses difference tones as a fundamental way of considering consonance and dissonance.
The amplitude of the voices is controlled by four potentiometers, each of which is associated with a pitch wheel. The combination tone’s amplitude is the product of the amplitude of the potentiometer of the two pitch wheels with which it is associated. They are triggered by pressing a button, laid out in a simple matrix, or by MIDI. Their buttons may be set to either latching or momentary.
Mutual Control
Pitch as symmetry.

Each of the four pitch wheels can control the others. Any wheel may be locked to any other, which then moves it in parallel or contrary motion. Parallel motion allows for the preservation of intervallic relationships; contrary motion allows for the discovery of new relationships. These settings provoke symmetrical configurations, as the contrary motion continuum, when laid out on a circle, creates symmetry around the tritone.
This idea draws on Dimitri Tymoczko theories, which are rooted in the observation that all pitch combinations can be reached via parallel and contrary motion. From this truism, Tymoczko generates a theoretical framework rooted in symmetries.
Further development
The instrument’s development has been driven by a desire to prototype as swiftly as possible. There thus remains much to be done that could improve the instrument.
First, its timbral capabilities are currently limited. The voices are split into three groups: the pitch wheels, the sum tones, and the difference tones. Each group can be assigned a wave form (sin, triangle, square, saw) and an ADSR envelope. In future, I hope to increase the timbral possibilities, both by creating a more effective interface for these settings and by adding further synthesis engines. In particular, I think that there is much promise in wavetable- and sampler-based approaches, as both have parameters that could be mapped to the pitch wheels, allowing for timbral difference along the pitch continuum.
Second, their interface could be improved. I will add LED rings and a screen to the interface, which will allow for visual feedback on the body of the instrument rather than on my laptop screen.
Third, the current version is digitally cumbersome. It involves two layers of programming: the Arduino chip and the Max patch. It is reliant on Max for digital signal processing, meaning that it cannot be easily combined into a standard audio signal flow. A future version would move everything on to the synthesiser’s on-board chip. This would allow for a much more flexible input and output system. An ideal configuration would include MIDI input and output, stereo output, 16-channel optical output, and a control voltage in/out for Eurorack compatibility.
Finally, it would make sense for this synthesiser to exist at multiple levels of complexity. While the fully featured version sketched out above would be my preferred performance interface, a more minimal version would be better for educational purposes. I have already prototyped a slimmed-down device, with three oscillators and their difference tones. Newer versions of this would build on the ideas above and on feedback from students to create an intuitive and fun way of exploring pitch and tuning.
This idea draws on Dimitri Tymoczko theories, which are rooted in the observation that all pitch combinations can be reached via parallel and contrary motion. From this truism, Tymoczko generates a theoretical framework rooted in symmetries.
Further development
The instrument’s development has been driven by a desire to prototype as swiftly as possible. There thus remains much to be done that could improve the instrument.
First, its timbral capabilities are currently limited. The voices are split into three groups: the pitch wheels, the sum tones, and the difference tones. Each group can be assigned a wave form (sin, triangle, square, saw) and an ADSR envelope. In future, I hope to increase the timbral possibilities, both by creating a more effective interface for these settings and by adding further synthesis engines. In particular, I think that there is much promise in wavetable- and sampler-based approaches, as both have parameters that could be mapped to the pitch wheels, allowing for timbral difference along the pitch continuum.
Second, their interface could be improved. I will add LED rings and a screen to the interface, which will allow for visual feedback on the body of the instrument rather than on my laptop screen.
Third, the current version is digitally cumbersome. It involves two layers of programming: the Arduino chip and the Max patch. It is reliant on Max for digital signal processing, meaning that it cannot be easily combined into a standard audio signal flow. A future version would move everything on to the synthesiser’s on-board chip. This would allow for a much more flexible input and output system. An ideal configuration would include MIDI input and output, stereo output, 16-channel optical output, and a control voltage in/out for Eurorack compatibility.
Finally, it would make sense for this synthesiser to exist at multiple levels of complexity. While the fully featured version sketched out above would be my preferred performance interface, a more minimal version would be better for educational purposes. I have already prototyped a slimmed-down device, with three oscillators and their difference tones. Newer versions of this would build on the ideas above and on feedback from students to create an intuitive and fun way of exploring pitch and tuning.