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I could get a good range of sounds out of the Mk I and Mk II but the knobs are touchy and it's hard to get back to a sound or tone once you've left it. So I decided to make a keyboard to recall different knob settings. This plugs into a control port on either Glitch Box, and by pressing a button, the corresponding knob is subbed in for either the interval or tuning knob. 8 seemed like a good number - enough for a one octave major scale or a 2-bar sequence. I needed a better enclosure than for the Mk I - luckily, where I work at NRG Systems, we were getting rid of some blemished enclosures for the iPacks we make.

First I marked out the holes with a sharpie on the inside and drilled them. Then I connected the 9V source points together. There are two 1/4 inch mono jacks. The sleeve is the 9V coming in, and the tip returns the control signal when one of the pots is connected via a button. I made two identical control jacks, so I can chain two keyboards together for a 16-button keyboard, or connect a Control Pedal to the spare jack to provide an offset for all the keys in unison.

I staggered the pots to save space, and it gave a nice effect anyway. I alternated button colors so it's harder to lose your place. Some tactile bumps might not hurt either for when you're not looking.

Done. Put it together with one of the other projects, and it's a handmade one-octave analog synth.
Patrick dubs this box the Excelsior 2000.

This project turns out to be a bit more expensive - pots and buttons don't come cheap. You can generally get a price break at 10 of a part. I would probably try a different button if I was starting over - these are nice and relatively big for the price, but you really have to mash on them to press down far enough to make contact. After playing for a while, your fingers get pretty tired.

Parts list:

Not much to this one. You can paste these into Mouser's BOM Import tool, then pick and choose what more / less you want. They may be outdated, just find something equivalent.

31VA505-F - 500k potentiometer. These are linear. Obviously if you are building a keyboard to control something else, just use the same value as whatever the pots will sub in for.

45KN013-GRX - Knob. It was cheap and looks nicely classic. Suit your own style, but make it fit 1/4 inch shafts and have a set screw.

112-R13-23A-Y or 112-R13-23A-R - Pushbuttons. This model also comes in other colors. You may want something different - see the note above.

502-11 - Mono 1/4 inch jacks