Tim Alex Jacobs' Orchestrion Puts Four Slide Whistles Under MIDI Control

Maker Tim Alex Jacobs has revisited an old project, a robotic slide whistle — building the Orchestrion, a robotic slide whistle quartet capable of semi-harmonious music under MIDI control.

"When I built the first robot slide whistle the plan was always to build a quartet of them, if time and budget had permitted," Jacobs explains. "[Electromagnetic Field 2022] was the perfect deadline to try and make it a reality. I submitted the idea as an installation, and got the thumbs up over a month before the event, but due to other commitments I couldn't actually start building this until two weeks before.

"I also gave a talk at the event (originally it was going to be two talks…) which meant I definitely over-committed myself. With the stress of trying to get the installation working, I ended up writing the talk on the morning I was supposed to give it, which was much less than ideal."

The installation, building on Jacobs' original single-whistle robotic instrument, sees fan motors attached to off-the-shelf slide whistles. A laser-cut wooden frame holds each whistle in place, with Dynamixel servo motors attached to arms which can move the slide in and out of the whistle under MIDI control. The four whistles making up the quartet are housed in custom wooden enclosures, two in the center and one each in the doors, with the motors and power supply hidden in the rear.

"A [Microchip] ATmega238P [sic] was used for the first slide whistle, with the code written in assembly. A beefier chip was needed to run four whistles at once," Jacobs writes, "and with the chip shortage in full force about the only board I could get at a non-inflated price was the 'Black Pill' STM32F401 (probably clone). The Raspberry Pi Pico had been released, but I hadn't tried one yet and switching to an unfamiliar architecture always comes with a risk. It turns out the Pico is very easy to use, but I didn't know that yet."

While self-admittedly rushed, the installation received positive feedback — despite some damage during the event and an issue with the whistles being somewhat out of tune. Attendees were invited to listen to pre-recorded MIDI tracks from an attached laptop, or to have a crack at playing the whistles themselves using a MIDI keyboard.

"I think the appeal of robot slide whistles," Jacobs surmises, "is mostly that we take an instrument that normally sounds terrible and with the power of computers we make it sound good."

The full project write-up is available on Mitxela.com, with source code published to GitHub under an unspecified license.