This Literal Drum Machine Rides on a Stroller to Festivals
Redditor JupyterJeff built a literal drum machine in a stroller that they can roll around festivals.
The term "drum machine" can be a bit misleading if you aren't acquainted with the devices. The name conjures images of robot drummers, but a drum machine is actually just a little device that outputs the sound of drums according to parameters that define the beat. The drums sounds may be recorded clips or synthesized on demand. If you're finding yourself disappointed by that reality, then I have good news: Redditor JupyterJeff built a literal drum machine in a stroller that they can roll around festivals.
Unlike your standard drum machine devices, this does resemble a robot drummer. Several drums, cowbells, and cymbals adorn the stroller and actuated drum sticks thump on them. Those can sync with music playing through speakers on the stroller to create a complete musical experience. JupyterJeff says that it is a big hit at events, where everyone that passes by gets excited and wants to see the thing in action.
It works by playing the drum tracks from karaoke files. A Raspberry Pi 4 Model B runs Rosegarden DAW (Digital Audio Workstation), which is software that includes many features, including a MIDI (Musical Instrument Digital Interface) sequencer and composition tools. JupyterJeff set up the Rosegarden software with two virtual devices: a synthesizer and a through port. A DAC (digital-to-analog converter) connected to the Raspberry Pi provides high-quality audio output for the synthesizer music.
The through port simultaneously outputs the drum track MIDI messages to a Python script that controls a Pololu servo driver board connected to the Raspberry Pi's GPIO pins. The Pololu board then activates the corresponding servos that swing the drum sticks. So Rosegarden reads the karaoke file and passes the drum track MIDI messages to the Python script, which plays the drums through the Pololu board. Meanwhile, the synthesizer plays the other instruments.
The result is a complete orchestra with "live" percussion, which isn't something you see packaged into a stroller every day.