What if you could twist a piece of sound in the air? With a little knowledge of SuperCollider, you can create your own live electroacoustic music with Greap (Grain + Leap) – an experimental interactive music environment. It started as a research project to investigate the gestural manipulation of sound events, and explore the affordances of open air interfaces.

The software is made entirely in SuperCollider, an open-source programming environment for sound synthesis and algorithmic composition. Greap also uses Geco MIDI to communicate Leap Motion data to SuperCollider through MIDI (though the next version of Greap will use OSC).

Greap uses granular synthesis implemented in SuperCollider – tweaking audio files (samples) stored locally in the hard disk of your computer. If you’re familiar with SuperCollider, you can load your own audio files and start manipulating them. Greap also uses the concept of presets, which you can design in advance of a performance in order to create a kind of musical structure. Through presets, users can design various interactive relationships between the gestures and the control parameters and create diverse musical outcomes.

The presets also include different cues for audio files that the user wants to manipulate without having to stop and start the performance. The control of the presets can be accomplished through an external controller, or through the GUI designed natively in SuperCollider. (Personally, I use a MIDI foot-switch.)

The musical structure of the piece is designed in advance of the performance. As a result, the music that occurs is semi-improvised by performing with the presets – allowing the user to improvise with the interaction possibilities and affordances given by each preset.

The source code for the project and other resources can be found on GitHub at github.com/KonVas/Greap. There you’ll find a simplified version that makes it easy to get started. To try it yourself, install SuperCollider on your computer, open the GECOMapSC.geco document with Geco MIDI, and run Greap.scd. Let me know what you think, and feel free to fork the project!

Konstantinos is a computer musician and PhD student currently researching new approaches to live electroacoustic composition.