Process Documentation
All of these projects utilized stepper capstan winches driven by an Arduino board. The capstan winches were used to drive fishing wire as part of an adjustable pulley system. The Arduino board served to communicate to a piece of custom software that translated inputs from an MPD218 MIDI pad into controls for the winches. The software included the ability to adjust variables in a synthesized spring/damper system to produce more organic movement. All of the movements seen in the video are a result of interaction with the MIDI pad and are live performances with no preset programming.
Details about this system can be read about here.
MIDI Pad 
Capstan Setup