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Electronic Organ

Discussion in 'Electronic Design' started by Rickydou, Jul 5, 2006.

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  1. Rickydou

    Rickydou Guest


    I need to find or design an Electronic Organ that would generate a full
    octave sound (DO-RE-MI-FA-SOL-LA-SI-DO) depending on which switch we
    press. Ideally an OEM module that could be intergrated in between our
    switches and the amplifier would be the best.

    Anywone would know where I could find this type of module or how to
    design this module using standard component?

    thank you very much!

  2. Luhan

    Luhan Guest

    Sinewaves or complex waveforms?

    Attack-Decay-Sustain-Release envelope?

    Monophonic or Polyphonic (how many notes)?

  3. Rickydou

    Rickydou Guest

    Hello Luhan,

    I just need to produce simple tone, so I assume sinewave would be
    enough... as for the envelope, you will have to excuse my musical
    knowledge... I'm not sure what to answer you...

    As for the number of notes, we would like to be able to play several
    note at the same time.

    Does it help you?


  4. Luhan

    Luhan Guest

    (please bottom post)

    The simplest method may be a microcontroller making square waves. I
    have gotten as many a 4 simultaneous notes out of a PIC - but you have
    to do the programming.

    Note producing systems are generally rated by the degree of polyphony -
    how many notes you can have at the same time. There is usually no real
    limit on the number of notes available.

  5. JeffM

    JeffM Guest

  6. Bob Eld

    Bob Eld Guest

    Pick up a cheap synthesizer like a Casio. They have many voices and most
    operate over four octaves or more. As was said above, don't re-invent the
    wheel unless you want the exercise in programming a micro or something. BTW,
    the eight note octave Do to Do is incomplete. A chromatic octave has 13
    notes not eight. C, C#, D, D#, E, F, F#, G, G#, A, A#, B, C. If your octave
    is not complete, you are very limited in key.
  7. Rich Grise

    Rich Grise Guest

    Strictly speaking, the "well-tempered" scale is one that's not an exact
    chromatic octave in any key, but "close enough" in _every_ key to get away
    with it. Each freq. is the lower one times the twelfth root of 2.

  8. Guest

    Err... the octaves in a well-tempred scale *are* exact, it's the other
    intervals that are approximations.

  9. Paul Burke

    Paul Burke Guest

    Even temperament means that the ratio between successive semitones is
    the twelfth root of 2, 0r about 1.0595. Only electronic instruments
    really get tuned that way though. Piano tuners bend the tuning quite a
    bit, particularly at the extreme ends of the keyboard.

    Paul Burke
  10. Ken Smith

    Ken Smith Guest

    Many years back pop-tronics (I think it was) had a design that used NE-2s.
    It only needed one RC and NE-2 per note. IIRC the signal was taken from
    the common point of all the capacitors.
  11. Rich Grise

    Rich Grise Guest

    OK, I misspoke. The _octave_ is a perfect octave, as you say, and it's the
    other notes - maybe I should have said, "chromatic scale" instead of

  12. Rickydou

    Rickydou Guest

    Thank you very much for helping me. You are right...I do not want to
    re-invent the wheel!

    I also found an IC that is specialized for this application: MOSTEK
    MK50240 Top-Octave Frequency Generator. I just need to find a supplier
    for this...




  13. Have you got a time machine?

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
  14. The MK50240 is outrageously and horrendously obsolete.

    Check the Ensoniq chips instead.

    But the magic numbers appear in my CMOS and TTL cookbooks.
    There is only ONE eight bit sequence that gets all of the notes right.

    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: email:

    Please visit my GURU's LAIR web site at
  15. Those things were so impressive when they were introduced, doing away
    with a bunch of oscillators or at the very least an oscillator and
    a bunch of small count digital counters. All you needed was an oscillator
    of the right frequency, and you'd get an octave of notes all with the
    exact ratio to the others that was required. More octaves were easy,
    since it just required a string of flip flops per note (or a more
    integrated string of them). Get that needed sawtooth to boot, with
    summing resistors of the outputs of the flip flops.

    But yes, things have leaped further since then. Last week, I found
    a small Casio "synthesizer" on a pile of garbage, sadly one black
    key is broken, which I intend to give to a one year old when he's
    a tad older. This is twenty or so years old, likely cost a fair
    amount when new, but they were doing polyphonic in that thing with
    a single IC (so I hear, I've not opened up), I think a CPU.

    It's gotten so easy that every computer basically has a full synthesizer
    built in, and top octave dividers are long in the past.

  16. Don't forget all your articles in Popular Electronics where you explained
    the insides of a synthesizer, about when top-octave dividers were the
    cat's meow, a big step forward from analog synthesizers, but only
    a small step in terms of what came later.

  17. JeffM

    JeffM Guest

    Get that needed sawtooth to boot,
    The wave shaping is actually done on the far side of the key contacts.

    (This requires only 1 key contact per rank per key.)
  18. Musically, the 50240 was an 'improvement' over 12 discrete out-of tune
    oscillators but it was not good. The intervals were all over the place,
    some notes sharp and others flat -- musically unpleasant. I replaced
    one with a raft of 74F chips running at 32 MHz instead of 2 MHz which
    managed to cross the boundary between 'appliance' and 'instrument'.

    I bought some organ samples from Milan Digital audio and re-sampled
    (tuned) using CoolEdit. You can hear an example here.

  19. Not any more.

    All the keys are scanned into a standard xy keyboard matrice.

    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: email:

    Please visit my GURU's LAIR web site at
  20. Obviously it's all done differently now.

    But even in your CMOS Cookbook, and your article in Popular Electronics
    that showed the basics of a polyphonic synthesizer using the top octave
    divider, you show ramps going to the VCAs, and those ramps were generated
    by summing the outputs of the ripple counters at the outputs of the top
    octave divider.

    And, a page of my copy of the CMOS Cookbook just fell out, 29 years
    after I got the book. That's the first of your books that have come
    apart, though I admit I likely have taken more care of them than
    some books. (On the other hand, the various TAB books I have have
    never fallen apart, but they've seen far less use.)

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