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OrganDuino: Open source MIDI conversion of old organ hardware

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  • OrganDuino: Open source MIDI conversion of old organ hardware

    So, over the course of a few years my significant other and I have created this: https://github.com/JDWarner/organduino - It's been working for some time, but I just now got the chance to clean up the documentation and make it somewhat more user-friendly.

    The basics:
    • Arduino Mega 2560, sketches included
    • Uses stacking Arduino shields with a PCB design which is provided and also open source
    • One stacking shield per manual/pedalboard
    • Designed for up to 5x 61-key manuals and 1x 32-key pedalboard, each transmitting events on a unique and easily set MIDI channel
    • Optimized sketch with extremely fast polling, imperceptible latency with 4 manuals and pedalboard all polled from a single Arduino
    • Debounce available, but we found it not required
    • Output via serial over MIDI (you need a bridge, like Hairless-midiserial, at least until you're very confident in your configuration)
    • Extensible, you can use this for 1-5 manuals and a partial pedal board up through a full 32 key AGO
    • Only designed for old hardware where all keys were wired to a single common buss (no digital keymatrices!)
    The last point is important. This won't work on any old organ, it has to be old enough to have common buss wiring. Our goal was to get to 4-5 manuals combining manuals from multiple organs, and so all of them had to share the same wiring approach as we were mixing manufacturers etc. This will not work for (relatively) newer organs with digital key matrix designs (every key needs its own wire).

    It bothered us that none of the available solutions for MIDI conversion of organ hardware were open source/hardware. Being starving students at the time, we scoured Craigslist for some old organs and started tinkering. Our project is now feature complete. A second Arduino can easily be wired to poll up to 61x6 = 366 stops, pistons, and finger buttons through separate MIDI channels.

    Expression pedal input is not directly supported, but PRs are welcome. We suggest this be accomplished on a separate Arduino.

    All info - hardware and software - available under the Apache 2.0 open source license. Hopefully some people find OrganDuino useful! If you build on this or find anything that can be improved, PRs are most welcome!

  • #2
    What a cool setup. Of course, I downloaded it for queue into my to-do projects.
    I mean, what if, let's say, a guy had, oh, I dunno, an old Polymoog sitting around...hypothetically speaking that is.
    Turn that keyboard into midi !
    Very cool.


    • physicsmajor
      physicsmajor commented
      Editing a comment
      This will absolutely work great with the buss-wired keyboards in most older synths. It's actually overkill for that, and might be so fast with just one board (plus the relatively hard immediate on sound from synths) that debounce would probably be necessary. The debounce example sketch provided only applies debounce to the pedal board, but this would be trivial to apply to a keyboard. If you want to do this and need any guidance, let me know (or make a PR with your synth sketch)!

  • #3
    This would work for an old MOS Allen digital too, but you'd need to first remove the diode matrix and stitch the several busses per manual together. Then simply wire to each of the 61 leaf switches where the diodes were formerly attached.
    *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!



    • #4
      Indeed jbird - if it's possible to get one wire per key all operating off a common buss, this project will take you from there! I haven't worked directly off the MOS series Allens. Our set of Allen manuals is considerably older, one generation away from pipes, and buss wired.


      • jbird604
        jbird604 commented
        Editing a comment
        The oldest MOS organs, possibly up through the early 80's, will have the individual leaf switches hand-wired, so one can easily clip off the existing wires and connect them up with a common buss.

    • #5
      How difficult would it be to get the sketch to work with the MIDIUSB library?


      • physicsmajor
        physicsmajor commented
        Editing a comment
        Should be as simple as swapping the imports and converting the call to send the midi events to the alternate library's syntax.

        You'll need to use some sort of shift register or otherwise as all of the compatible boards have less pins than the Mega 2560.