Update: Another via Inverse Room in the comments. Cool, thanks Inverse Room.
"I just reviewed the Triwave for TapeOp...it's really a fun box, but people should try to build their own! 4ms gives out the schem and layout for free"

Title link takes you to an interesting little sound device. More info below and at the site. Via
this Music Thing post on the Glasstone Tin Can.

"triwavepicogenerator contains two tone generators... and three variable speed
point slow eight cycles per second to two hundred cycles per secondlow frequencie oscillateurs that independently vary the pitch of each tone generator...
controls:
red, yellow, green speed (three low frequency oscillators)
red,yellow,green linnet depths
red,yellow,green gale depths of effect of each tone generator by each oscillator...
...control the center pitches (linnet, gale) of each tone generator
mix between volumes of each tone generator...
control the master volume
..each channel's tone switches between square and triangle wave audio outputs...
lfo range extends into audio frequencies for faux ring and veri-beat modulation"