Here is a rough block diagram of what I have in the Tone Organ. A modified 555 based osc, a 555 LFO, and a drum toy. The osc can be modulated by either the LFO or drum toy, or it can play unmodulated thanks to a SPDT center off switch. On the drum toy I replaced the speaker with an LED which blinks on a photo cell to modulate the osc. The LFO I originally got from the PAIA archives and slightly changed it. The osc itself is a basic 555 from Forrest Mims with 8 caps (each with a mom sw between gnd) instead of 1 cap, and both res received atleast one pot in series.
Samples can be found on Instruments page.
The original toy piano.
Midway through project.
All painted up pretty.
(L to R) Power on/off, LFO/plain/drum, LFO knobs and switch, and lastly LFO LED.
Knobs & slider = pitch control. Alum plate = toy drum controls. Acorn nuts = bond contacts.
Relocated the speaker to a leg, drilled holes, and added vol control.