Use your keyboard to play on the virtual OP-1 at op1.fun. This allows you to play a polyphonic melody instead of individual notes and better understand the sound of the patch. In addition, you can use this extension on your computer when the OP-1 is not at hand. The QWERTY... and 234679... keys cover 20 notes. The extension is not affiliated in any way with Teenage Engineering or op1.fun.