Robotic entertainment troupe performing for your enjoyment


This page documents the wonderful and winding path of Grumpenspiel, my robotic entertainment troupe. It is a group of MIDI synthesizers that make music and display light FX. Some fun costumes and stage decorations complete the party.

Grumpenspiel makes music by moving motors to hit, pluck, and rattle stuff. This differentiates it from many robotic systems that generate synthesized electronic digital music or play sampled sound clips.

The goal of this project is to explore art that weaves together many disciplines including music, electronics, mechanics, programming, robotics, lighting, tailoring, etc to create a fun (A) outlet for the maker and (B) experience for the audience.

Here’s a video of very early prototype proof of concept that got the ball rolling. A nice blooper reel to watch the $3 servos quickly come out of calibration….

Grand Vision

The grand vision for Grumpenspiel centers around a pouting cat playing the xylophone. The image formed in my head, amused the hell out of me, and it grew from there. A good music act needs some supporting instruments, along with fun characters to play them. Light shows make any concert better. Dancers, robotic of course, round out the show.

Each of the pieces is a stand alone module. This allows for incremental building, giving me a continuous stream of accomplishment. Finishing each component is satisfying and can immediately wow and amaze friends, family, and the Internet. Modular design also allows each component to be used in new and unusual ways. For example, sticking with MIDI standard communication lets me take an instrument out of Grumpenspiel and hook it up to any old keyboard MIDI controller.

Audio Synths

These modules produce the sounds that make Grumpenspiel fantastic. It is a growing list, and many more ideas can be found in the Future Parking Lot at the bottom of the page:

  • Demonic Tapioca - lets make some noise. A single small servo motor, MIDI input, tap on something that sounds fun. Dress up like a necromancer
  • Cow Baby - Two drum sticks powered by servo motors, a slick looking wooden chair, perfectly sized for my niece’s favorite doll, Cow Baby

Visual FX

These are the dedicated visual FX that make it more fun to watch Grumpenspiel jam. Some of the Audio Synths above include their own light shows, but these listed down here are specifically visual.

  • Noisy Blinker - Sound Reactive Light, microphone listens to sounds, makes fun lights
  • Simple MIDI LED - a basic proof of concept to react to MIDI IN messages
  • First Light Sculpture - light FX with a few LED elements housed in custom sculptures, controlled via MIDI


This section is for the control modules that instruct the audio and visual pieces what to do.

  • MIDI Mud - MIDI Step Sequencer, looping over 8 notes and 2 instruments
  • Servo Slam - tuning device that sends MIDI SysEx messages to configure the motor positions of instruments


Some behind the scenes infrastructure that helps the instruments deliver the fun. These modules are pretty technical, not full of pretty sounds and sights like up above. If you like voltage regulators and Schmitt inverters, then this is the place for you:

  • Power Thru - MIDI Thru box that merges and splits messages and provides power over MIDI
  • Micro-PT - a smaller version of Power Thru, this provides 1x2 MIDI THRU splitting
  • Midler - Robust MIDI IN header to assist with developing synths and light FX
  • Mission Control - Raspberry Pi 3 B+ is the conductor of this orchestra

Future Parking Lot

Here is a parking lot for additional ideas. I jot them down here, maybe expand a bit on them later in this file while dreaming and brainstorming, and then move them up to the list above when they are more thought out.

  • One xylophone player, the Frowny Feline, with three mallets, one each front paw and a tail.
    • apply some logic behind the note distribution, allowing for some nice polyphonic chords.
  • Percussion section, a variety of tapping motors and jingling bells
  • Something that plays some more bass notes.
    • bass guitar plucker
    • pvc pipe resonator
  • Simple tone generator - i’d like as little synthesized sound as possible, but there’s always room for a custom wave generator to bring an 80’s synth feel to the show.
  • Simple lighting effects
  • Complex lighting effects
  • LED scrolling marquee
  • Dancing robot(s) - line followers that go around the stage, connected via 433 MHz or Bluetooth wireless
  • Robot on a track with some visual FX or a spotlight to shine on other instruments
  • POV spinning LED array(s)
  • Windmill clap hands
  • Android app to let me at least visualize some of the show, if not control it
  • Web interface to allow audience browsers to see something fun (or even interactively add fun stuff like text to the marquee, or each audience member gets to control a piece of lighting)
  • Design a fun logo, because after all, branding is everything!

MIDI Definitions & Standards

This section is of most interest to other MIDI buffs or tinkerers.