School Rhythmer - peg/matrix 'programmable' drum machine

video upload by wildchurch

"This is my take on the (very rare) Kawai School Rhythmer...an educational rhythm machine from the 1960s.

Rhythms are programmed by inserting pegs into a matrix sequencer - thereby offering a highly visual indication of how a rhythm is formed.
Presumably, it helped children like myself to feel the 'magic of beats'...

I've never actually seen or heard a fully functioning original, so aside from the aesthetics being different, I've used some guess work to replicate the percussion sounds, as well as the functioning of the 'Hyōshigi' trigger - for my build, this works as a 'fill' switch when a pegs are inserted in the matrix. With no pegs inserted, this triggers the Hyōshigi voice alone.

Additional features include a clock divider (1/2 & 1/4 time), clock in/out and a gate out for sync'ng with external devices.

The original sports five percussion sounds:
- Triangle
- Hyōshigi ('Japanese woodblocks')
- Cymbal
- Small Taiko
- Big Taiko

There are two additional voices which can be selected via switching on the circuit board:
- Hyoshigi can be switched to HiHat
- Small Taiko can be switched to Snare

For my build, the drum sounds are based on the circuitry of a 1970s DIY drum machine kit produced by the Japanese company, Elekit. The schematics for which have been updated and reproduced by Gadget Factory, to whom I am most grateful for making them available:
http://park19.wakwak.com/~gadget_fact...

The remaining circuitry is built around 4017 chips and a 555 timer for the internal clock. The peg matrix involves microswitches, such that, when a peg is inserted, the signal passes through, triggering a drum sound on that particular step.

There are easier, groovier ways of generating rhythms - this is as much a 'sculpture' as a musical device..."