Topsy - A very compact MIDI Organ (20-64 notes)

by John Smith

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Scales for the Topsy Organs

Many builders of my designs have been showing an interest in making a MIDI organ. My latest creation has turned out to be a remarkable little organ, so I have prepared a document giving details, in which I have tried to include all the information a first-time MIDI organ builder would need to know.

Topsy started out to be a 20-note motor driven organ. To get the best efficiency I used bellows driven by a wheelchair motor, which on completion seemed big enough to drive a bigger organ.  One thing led to another and I ended up making it to play the 65 key music I use on my Dance organ.  In reality there is not enough wind for some of these arrangements but the majority are fine. The popular 46/48-key scale uses the same notes and so these can also be used.  In fact the organ could be made as a hand-turned one and this would work very well.   The final specification is 64 MIDI keys, 78 pipes, 3 registers, triangle and wood blocks.  The simple Glockenspiel is the same as the Universal design and simply unclips from the front of the organ for transport.  The organ runs for 7 hours on a 12 volt 30 AH battery and measures approximately; 24 x26 x 17 inches, including battery. The instructions apply equally well if you intend to build a smaller louder organ or even a parlour organ.

The information pack I have prepared is intended to be used in conjunction with my Universal Plan. It is not a building package in its own right, more a description of how I made this lovely little organ out of odds and ends, it should be seen mainly as inspiration for other Amateur Organ Builders.

Having made Topsy and found it to be a very nice organ, I disassembled it and produced a 1 hour video showing the essential parts, also a simple MIDI reed organ and a tune on my 98 MIDI Dance organ.

Drawings are shown for the double acting bellows, windchests, solenoid valves and all pipes. I have tried to explain the MIDI system as it applies to fair organs including some basic wiring diagrams and practical tips as well as a circuit for register control. This is all done at what I call an "Everyday Electronics" level. Two methods of control are discussed, the John Wale decoder and Alan Pell's Harmonette system.

Building a MIDI organ involves up-front costs for the electronics, valves and blower, these can be quite expensive. The methods I describe should enable a MIDI organ to be built for approximately £200.

This information pack consisting of 8 sheets of written information, 7 of drawings and the 1 hour video is now available, price £20 incl. UK Postage.

Contact: John Smith

Topsy scales for which I supply music

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