MIDI Controller is an Interaction block. It allows you to create playable synths by letting you trigger any connected Source blocks using a connected hardware MIDI device. Hardware MIDI devices commonly take the form of a keyboard, or a set of trigger pads, and will connect via USB. They control music hardware or software via digital messages.
Support for MIDI is currently Google Chrome only.
It’s options let you switch the ‘Voices’ between monophonic or polyphonic. ‘Octave’ sets a transpose up or down across all connected Source blocks, and ‘Glide’ sets the time it takes for the pitch to transition, or glissando between notes, when in monophonic mode.