Hardware 1 – DSP Boards

What hardware microcontrollers and DSP chips are readily available to power the Interface module? That is a central question to start working on ways to implement MIR algorithms into a module. The second question is what code language is compatible with the chips and how can one implement it.

Those questions are examined in a paper by the International Conference on New Interface for Musical Expression (short NIME) named: „A streamlined work ow from Max/gen~ to modular hardware“ by Graham Wakefield, 2021 which focuses on the oopsy workflow which streamlines digital sound processing algorithms to work with the modular synthesizer environment.

As microcontrollers such as Arduino and Teensy get more powerful by the day they are more and more useful for musicians and luthiers to use in music and musical instruments. The play to make electronic music live and without a laptop that would run a DAW is a strong motivation for musicians to get into coding and learn to develop equipment which is providing often the few tools a DAW is offering them for live performances.

For DSP chips to read code programmed in a visual language like Pure Data or Max MSP the patch most of the time has to be compiled into C++.  Within Max, there is for instance the [gen~] object which is capable of doing so. To implement the mach well into the hardware ‚oopsy‘ was developed which streamlined the workflow, to get an algorithm onto hardware, with a targeted firmware generation that is optimized for CPU usage and low memory footprint and program size, with minimal input required.

Electrosmith Daisy:

Processor: ARM Cortex-M7 STM32H750 MCU processor with 64MB of SDRAM and 8MB of

flash memory, IO: Stern, 31 configurable GPIO pins, 12x 16-bit ADCs,  2×12 bit DACs, SD Card interface, PWM outputs, micro USB port (power and data), Dasy Seed: 51×18 mm

Dasy Seed © electro-smith.com

It is a common microcontroller in Modular Synth gear today. The MCU processor is with its maximal 480MHz quite capable and the AK4556 Codec has AC-coupled converters that internally run with 32-bit floating-point. Daisy firmware can be developed using Arduino, FAUST, PureData via Heavy, as well as Max/gen~ using the Oopsy software. internal latency down to 10 microseconds.

Bela Beaglebone:

Bela is an open-source platform based on the beaglebone single-board computer design for live audio. It is compatible with Supercollider, PureData, and C++. It is optimized for ultra-low latency, with 0,5 ms it is better for desktop, cellphone, Arduino, and Raspberry Pi solutions.

Bela Staterkit © Bela.io

Owl Programable platform

8kHz to 96kHz sampling rate, 24 bit stereo codec, 3500 operations per sample @ 48kHz, Powerful STM32F4 microcontroller: 168MHz 32bit ARM Cortex M4, 192Kb RAM, 1Mb Flash memory, Integrated DSP, FPU, DMA, 1Mb 10nS SRAM, USB MIDI

Rebel Technology, OWL Digital mk2 Rev 7 © https://shop.befaco.org/misc/1091-rebel-technology-owl-digital-platform.html

IO Eurorack module: 2 audio inputs, 2 audio outputs, 5 CV inputs, 1 gate/trigger in, 1 gate/trigger out, 1 USB Type B connector


Graham Wakefield. 2021. A streamlined workflow from Max/gen~ to modular hardware. Proceedings of the International Conference on New Interfaces for Musical Expression. http://doi.org/10.21428/92fbeb44.e32fde90.




Reference 2 – Expression Hardware


In modern Midi keyboards, there are several possibilities to record expressions. The widest spread feature is the velocity control. This parameter is controlled by the velocity one hits the keys and thus can be easily added by keyboard performers in their playing like they would playing an acoustic instrument. With the synthesizer and the possibility to create the sound of the instrument individual to the performance also came the possibility to control parameters of a sound which in acoustic or electro-acoustic keyboard instruments with keys and pedals only really possible. The Pitch and Mod wheel were introduced to make such changes possible. The first was a spring-actuated week or stick which was mostly used to modulate the pitch like with a guitar. The other was an adjustable heel with which one could send fixed values or modulate them manually. The fourth modulation source developed for keyboard synthesizers is aftertouch. As the name suggests, it is applied by altering the pressure after the key is depressed. This can be applied mono- or polyphonically.  All of those controls added to the expressivity of synthesizer performances mostly. Only one of those controls is determined before the tone or as the tone is generated. The others are applied in the decay of the sound. So those are 4 control values that have been proven to add expressivity in performance. 

Ofcourse, these weren’t the only tools that were developed to do very expressive performances, although they are the most common ones. There is a multitude of midi controllers to add expression to an electronic music performance. The expressive E ‘Touché’ or ‘Osmose’, Buchla and Serge capacitive keyboards and joystick-controllers on synths like the EMS Synthy, Korg devices like the Sigma or the Delta and as controller module for Eurorack-, 5U-, Buchla- and Serge-modules. 

Other Concepts

Then there are control surfaces that take another approach to the whole concept of the Keyboard entirely. These Concepts go often but not always hand in hand with a synthesizer engine.

HAKEN Continuum

The Haken Continuum for instance is a Synthesizer with a control surface that can detect movement in 3 axes.

The Haken Continuum Fingerboard is an instrument born to be as expressive and as rewarding to play as an acoustic instrument. The uniquely designed sensitive playing surface has been symbiotically merged with its powerful synthesis sound engine to produce a truly unique playing experience. The  Continuum is a holistic electronic instrument that puts its player at the heart of a uniquely fluent, gestural and intuitive musical playing experience.


Roli Seaboard

The Roli SEA Technology which is implemented in rolis seaboard controllers is as roli puts it:

“Sensory, Elastic and Adaptive. Highly precise, information-rich, and pressure-sensitive. It enables seamless transitions between discrete and continuous input, and captures three-dimensional gestures while simultaneously providing the user with tactile feedback.”


Roli Seaboard Rise 49


The Linnstrument is a control surface developed by famous instrument designer Roger Linn. Interesting here is the approach to not apply a piano-style keyboard but rather use a grid-style keyboard which rather reminds of the tonal layout of string and guitar instruments. With the linnstrument there is also a release velocity recorded which places it even more into guitar territories where pull-offs, when one rapidly pulls of the finger of a string to excite it and thus making it sound, is a standard technique.


So few of the looked at control surfaces if any have more than 4 modulatable values. This would be then a minimum for a module that should be able to translate the expression of an instrumentalist into control voltages.

Reference 1 – Sarah Belle Reid

Copyright © Sarah Belle Reid, twitter

Sarah Belle Reid is a Trumpet player and Synthesist who takes the sound of her brass instruments and puts them through her modules Systems like Buchla, Serge, or Eurorack. She has developed a device with which she translates her trumpet playing to CV and/or MIDI messages called MIGSI.

They Developed MIGSI in a big part to enable her to use all of the techniques Sarah Belle Reid has developed on her Instrument to translate into more than ‘just’ her instrument and open the horizon of the instrument the electronic music-making possibilities.


MIGSI: Minimal invasive gesture sensing interface. She calls it ‘electronically augmented trumpet’ too. The device was co-developed by her and Ryan Gaston around 2014. They also founded ‘Gradient’ a joint venture between them where they develop “handmade sound objects that combine elements of the natural world with electronic augmentation.” (vgl.: Gradientinstruments.com).

Migsi is a Sensor-based Interface with 3 types of sensors and 8 streams of Data. Pressure sensors around the valves which read the pressure of the grip force, an accelerometer that senses movement of the Trumpet, and optical sensors which reads the movement of the Valves.


The hardware is then read by a MIGSI app which is a MAX map Patch. The app is used to process thee the audio signal of the trumpet, modulate external equipment with the sensor input or modulate a synth engine inside the MIGSI App.

(vgl.: https://www.youtube.com/watch?v=tbXgUDQaNv0)