Giving MIDI Organs MIDI Drawbars

This goes back to Bach: if you want to change the sound an organ makes, you have to pull on some drawbars. This design didn’t change for 300 years, and in the 20th century with the advent of ‘tonewheel’ organs, you still had small bars to pull to change what sounds came out of the organ. While this was a simple solution for air-powered organs of the 1700s, when it comes to MIDI, rotary pots are a lot less expensive than linear pots. Given the lack of drawbar MIDI controllers, [Stefano] decided to build his own. It has nine drawbars and eight buttons, all connected to MIDI.

The interesting electromechanical part of this build, the drawbars themselves, are ripped from a Hammond organ. Don’t worry, plenty of these were made and only a handful actually sound good. To that, [Stefano] added a few pushbuttons soldered onto a piece of perfboard, and everything is wired up to a Teensy LC, the microcontroller platform that’s becoming the standard for everything from MIDI controllers to computer keyboards. MIDI over DIN and MIDI over USB are supported, and all the buttons and drawbars are individually programmable. You can even do that through SysEx messages, because that’s how things were done back in the day.

While there are a few MIDI-controlled organs that still use drawbars — the double manual Nord comes to mind imminently — this is a great solution to putting drawbars into anything that speaks MIDI, VSTs included.

Retrotechtacular: The Hammond Novachord

Just when we thought we’d heard of all the cool early synthesizers, a tipster rattled our jar with news that someone completely restored a Novachord. These spinet piano-shaped prototypical synthesizers were made by Hammond for only four years. About a thousand of them were built before sales sagged and parts became scarce in 1942. It is estimated that only 200 or so are still around today.

The Novachord’s sounds are generated by a bank of twelve monostable vacuum tube oscillators. Each one is tuned to a pitch of the chromatic scale in what is called divide-down architecture. [Hammond] and his co-creators [John Hanert] and [C.N. Williams] used the property of dividing a frequency in half to generate the same tone, but one octave lower. This design means that all 72 notes can be played at the same time. Adjustable formant filters shape the often otherworldly sounds, which are then passed through flexible tube-based envelopes.

[Phil] knew it would be a big job to restore a Novachord in any condition. Thousands of passive components all had to be replaced. The cabinet bore all the hallmarks of a well-used parlor instrument—water rings from cocktails, scratches, and cigarette burns galore. [Phil] says that woodworking really isn’t his thing, but he did an outstanding job nonetheless of sanding every nook and cranny and applying several coats of stain. There are tons of drool-inducing pictures on his project site, and several clips of [Phil] really putting it through its paces.

Thanks for the tip, [Mike]!

Retrotechtacular is a weekly column featuring hacks, technology, and kitsch from ages of yore. Help keep it fresh by sending in your ideas for future installments.