The GREEN and BLUE dials of the MOTION track (right-most track) control speed and fading respectively.
- Plug in your OP-Z into your computer
- Make sure it's set to output midi (I used the iOS app to do this)
- Click on the connect button
Uses OPZ.js to parse midi. A link to the code can be found in the libary's example section.
Unfortunately Web MIDI is supported by a limited number of browsers. tl;dr, I'd recommend using Chrome.