Tonewheels Warble In This Organ-Inspired Musical Instrument

Younger readers may not recall the days when every mall had a music store — not the kind where tapes and LPs were sold, but the kind where you could buy instruments. These places inevitably had an employee belting out mall-music to all and sundry on an electric organ. And more often than not, the organist was playing a Hammond organ, with the distinct sound of these instruments generated by something similar to this tonewheel organ robot.

Tonewheels are toothed ferromagnetic wheels that are rotated near a pickup coil. This induces a current that can be amplified; alter the tooth profile or change the speed of rotation, and you’ve got control over the sounds produced. While a Hammond organ uses this technique to produce a wide range of sounds, [The Mixed Signal]’s effort is considerably more modest but nonetheless interesting. A stepper motor and a 1:8 ratio 3D-printed gearbox power a pair of shafts which each carry three different tonewheels. The tonewheels themselves are laser-cut from mild steel and range from what look like spur gears to wheels with but a few large lobes. This is a step up from the previous version of this instrument, which used tonewheels 3D-printed from magnetic filament.

Each tonewheel has its own pickup, wound using a coil winder that [TheMixed Signal] previously built. Each coil has a soft iron core, allowing for the addition of one or more neodymium bias magnets, which dramatically alters the tone. The video below shows the build and a demo; skip ahead to 16:10 or so if you just want to hear the instrument play. It’s — interesting. But it’s clearly a work in progress, and we’re eager to see where it goes.

9 thoughts on “Tonewheels Warble In This Organ-Inspired Musical Instrument

  1. Since the creator asked for other things to do with a pickup … I recently tried holding a tuning fork up to a pickup and got some nice results. Positioning is super fiddly, though. Basically an electric celesta.

    I could drive an electromagnet (without a permanent magnet) to cause the tuning fork to ring, and extract that energy either with just a conventional sounding board, or stop the high-voltage electric drive and then use the electromagnet as a pickup by applying a DC bias.

  2. I heard a story that Hammond was a clock manufacturer that lost it all in the depression and an enterprising engineer repurposed the gear making machines to make tonewheels for a cutting edge technology electronic organ.
    Another good 3D printer project could be the rotating horns for a Leslie tone cabinet used with the Hammond organs.

  3. Most of those mall stores were Lowery Organ. The story I’ve heard (NAMM) is Hammond had the market with the tonewheel design, and held it for 20+ years in mom and pop stores. In 10 years Lowery in malls across America wiped them 90% to 10% organ sales, with electronic oscillators and then keying (attack-decay).

    The Mall experience, caramel corn or Cinabon and Lowery organ muzak!

    Interesting that Hammond which had THE electric clock at the time went down with the Crash, but institutions and churches needed an organ that didn’t need air etc. They hurt less than the man in the street. Radio was big and only a few giant stations had a pipe organ. Hammond him self realized that the teeth of gears made “sounds” to pickup and ran with it.

    1. Hammond also made non tonewheel organs they used to target the home market and they sounded nasally and really bad, much like most of the other brands. At the time there was nothing on the market that was anywhere even slightly close to the Hammond organ. They completely dominated the church market and there really wasn’t anything else for professional blues, jazz and rock musicians. Where would we be without Booker T and the MGs, Procol Harem (Lighter Shade of Pale), Steppenwolf, Emerson Lake and Palmer, Jimmy Smith, Allman Brothers (Whipping Post, etc.)Young Rascals, etc, etc.none of which would be what they are without the Hammond. Granted there was the odd Mellotron and Farfisa combo compact with the funny keys, but nothing ever really compared to a B-3 with the legs sawed off and plywood nailed to the bottom or a porta-B.
      You can still see 50 year old B3 on SNL when their band plays and when they bring out real musicians.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.