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This video shows two casio keyboards, a drum toy, switch sequencer, mini modular synth and analog sequencer all linked together. 
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I built the modular synth and sequencer based on schematics from 
<a href="http://www.musicfromouterspace.com/">http://www.musicfromouterspace.com/</a>
If you want to get into building analog synth gear, but don't know where to start, go to this site!!!
Super helpful, tons of info and he has lots of circuitboards for sale.
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The switch sequencer is the blue box second from the left. This is the central brain for this whole operation. Schematics for this piece can be found <a href="http://www.casperelectronics.com/finished-pieces/sequencers/step-sequencer/">here</a>.
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This is used to trigger the drum toy (rehoused in the brown box to the left) and is also triggering the casio keyboards which are pretty quiet in this video. 
The switch sequencer is also outputing a clock pulse which is being fed to the analog sequencer which is controlling the analog synth.
What you get is a link between circuit bent instruments and analog synth gear.
<a href="http://www.casperelectronics.com/images/finishedpieces/MiniModular/S3600011.JPG"><img src="http://www.casperelectronics.com/images/finishedpieces/MiniModular/_S3600011.JPG" width="400" height="534" alt="" title=""  /></a>
