Radical ring modulator
The M.A.S.F. Swan Song is an excellent ring modulator in a foot pedal (treadle) enclosure.
It's designed to go well with the frequency range of a guitar but is also useful for good ol' noise making!
Step on the pedal forward to get higher pitch sound and back to go low.
Operates with a standard 9-volt battery or a 9-volt DC 'barrel' type tip negative power adapter.
Check out this video on YouTube.