Introduction to the Mellite computer music environment. Part 14: GPIO - accessing the digital input and output pins on a Raspberry Pi, the example being a button box and using a relay to route a sound signal to different speakers. Towards the end, showing how to start and parse system or shell processes, and passing key/value properties to Mellite and using it within a control program.

This is based on Mellite v2.49.1. See https://www.sciss.de/mellite/ for details.