Groovetube - plasma waveforms

video upload by Telmatronics

"Scope trace showing output sound waveform.
Plasma fluctuations can have a range of bizarre waveforms, such as alternating long/short periods and repeating but irregular patterns. Here the drive is varied with each note, and you can see different types of waveform interact with different input tones.
This clip also shows some first testing of an auto-tuning system.
In this, the machine first listens to the tube output to learn how to drive it to be in tune with applied input tones. Plasma does not have a linear response to drive conditions, so the system doesn't always produce exactly the same result."