SO-666 is a feedback based drone synthesizer building upon the SO-KL5 synth.
It creates haunting cacophonic howls and drones.
It's a bit hard to play but making good use of the modwheel will help keep the
sound in control.

SO-KL5 is a string based "piano" synthezizer. The strings are
modeled using the Karplus-Strong String simulation method.

SO-404 is a simple bass synthesizer using 1 oscillator and 1 filter.
The oscillator is a simple saw wave oscillator and the filter is a simple
resonant lowpass filter. You know, like that other very good and famous synth
with a similar name. Just not as good and famous.