This is a Faust implementation of a 1969-designed Yamaha combo organ, the
YC-20.  In addition to the Faust code, it has a Gtkmm UI with Jack audio
and midi support.

Original YC-20 organs have a touch vibrato control, which is vibrato induced by
horizontal movement of the keys. As there very few (almost none) midi keyboards
which produce such information, this feature has been left out of the emulation.
Instead of the touch vibrato control, the control panel hosts a "realism"
switch.