This is just holding down one key. A 64-segment envelope is used somewhat like a sequencer, controlling both pitch and whether there's sound at all. It also shows off the envelope's ability to loop, and to go to some other segment on a trigger (in this case going to segment 40 upon key release).

Note the sound is recorded directly from Moselle: no hardware or external processing was used.

Devs, Prods & Tags: Moselle SynthesizersMoselle