How to Build Techno Music Robots
Dear Reader,In this article I will explain the technical background of my techno music robots. Maybe you have seen my giant MR-808 Robot. Thats where I started dealing with Robotic Electronic Music (R.E.M.) on a daily basis. Since then my whole life is dedicated to experimenting, building and playing shows with music robots. I wake up with them in the morning and think about music robots at night. Why? Because I think that electronic music has to evolve and I am very bored with music synthezisers, modular synthezisers, samplers, and computers. I want Future! Robots! And Techno!My music robots always consist of four parts:
- The Electronics (PCB with MIDI-In, Mosfet, )
- The Mechanic Actuator (Motor, Solenoid)
- The Acoustic part (body, tongue, drum, string, mallet)
- The Amplification (piezo mic, pickup, Microfon)
The Electronics
The Electronics are used to create an electric pulse out of a MIDI Signal, so that the actuator (motor) starts moving.The electronics normally consist of an ATMEGA328, an MIDI-IN, an logic level MOSFET (e.g. IRLZ34N or VN820P) and something to drive the lights (an TLC5940 or just some small Mosfets)I started building my electronics on breadboard but as the china PCB manufacturers like EasyEDA got so incredible good and inexpensive I couldn’t resist using that part of globalization as well.
The general setup is like this:
I use only MIDI notes with velocity to control robots. Throughout the years and performing solo on big stages, on rainy festivals, with broken cables and in a hurry, and working with a lot of other artists like Mouse On Mars I learned that the simpler, the better. No CC Commands, no OSC, no complication.To control the volume of my robots I use Velocity Through Impulse Length Control (VILC - I made up that term, haha!). This means that with mapping the MIDI velocity to the length of an electric impulse for a motor or solenoid you can actually control the acoustic volume. Other music robot builders like (Dada Machines) or Polyend use this technique, too.In music robotics it is very important to work with visual key elements, so it is visible what is actually happening. Either one works with very big movements - this is nice, everyone can see whats happening. But it has the disadvantage of very high latency and normally theses robots are hard to transport. The other option is to add light to a very small movement. I chose this option, which after my knowledge Uk based Robot artist Felix Thorn introduced in the mid-2000s. Like this, my robots have a latency of 5-20ms (from MIDI note to acoustic signal) so you can actually play them live! But the movement is only a few milimeters, so I added a pulsed Light (fade out) to make it more visible. When I perform on bigger staged I also use a dedicated multicam system so everyone can see whats going on.
The Mechanical Actuator
So, you want to move something in the real world. For me, Pneumatics is out of question (Compressorhead for example are robots based on pneumatics). We all know, that air pressure or even better hydraulics (oil) actuator offer a much better power density then electric actuators like motors. But you need generators to create the pressure and they are very very heavy. In contrast, Electricity is everywhere.So I am using: Motors, Solenoids, Servos, Stepper Motors, and electric fields to move stuff!I am mostly purchasing motors or solenoids from ebay and a german supllier called pollin electronics. Whatever works! 
The Acoustic Part
Now comes the most important part and the one that needs most experimentation and expertise: To find something that sounds good. I recently found out that I am a sound hunter! For years already I constantly look around for things that have a special sound to them. Often they are not even music instruments - I try to find a hidden use in an object that was not meant to be used as a music nstrument. True hacker spirit!Percussion Robots are the most easiest and robust robots to build, so my robots make up 80% of them. I use, metals, Glasses, tongues, kalimbas, strings, hard drives .. anything that vibrates. A very good ressource is the book “Musical Instrument Design” by Bart Hopkin.Here is an example: You know, bass is the mother of all sound, so we need a lot of bass. With acoustic instruments this gets big quite quickly (5m Organ pipes, anyone?). So several years ago I wanted an 808-ish bassdrum sound. I experimented with different objects (a real drum, a string ..) and ended up using a kalimba with a piezo mic. What a wonderful, warm, round sound!So for my installation Tripods One I developed this Futuristic Kalimba:
- 0.8mm Spring steel metal tongue
- Piezo Microphone
- 3D printed holder to adjust everything
- Solenoid 24V / 5A from Schulz Magnets
With the length of the spring steel you can change the pitch of the instrument. I ended up using five different tongues for different tones. With an optional Piezo High-Z amplifier nothing can hold you back - the most beautiful robot bass drum sound on the world.
What I want to do to improve this is using a special made corpus that supports the frequency of the tongue. Every body has some main frequencies to it - you know that from an empty room with a standing wave, or from an empty bottle wher you beat on. A normal instrument builder would avoid that: A guitar body for example tries to have more softer body-frequency spectrum with little spikes. But we can uses that to support our main frequencies of our bass drum tongue! Longer decay and a softer tone. I am currently building such a tuned body and will keep you posted about the progress.
Amplification
There are different philosophies of how to approach the sound in music robotics. Some artists don't use amplification at all and work only with the natural sound. This is somehow the master-league, because it involves a lot of knowledge about acoustic instrument design.I use amplification, to even out the different volumes of the many instruments, but also because I play electronic music and that has to be loud.When using direct microfones like SM58 or C414 it is easy to capture the main sound of a music robot. But on biggers stages this easily gets a feedback-disaster. So I am only using contact microfones. You can build them yourself, and they are pretty cheap. The issue here is, contact mics take only direct vibrations inside a body - you can not capture air pressure differences (like normal mics). For some instruments that doesnt work. All flutes, woodwinds etc. are hard or impossible to catch with a contact microfone. But hey, we are talking about techno here, and we wouldnt want pan-flutes there anyway! 
The placement of a Piezo Mic is most important. Sometimes 1-2 milimeters make the difference. Then there is the pre-amplifier. You can plug a piezo mic directly in any line or mic preamp. But as piezo mics have a very high resistance, the will create a high pass / lowbass with any standard input, so the sound gets “phony” - no bass, and highs. When you uses a High-Z piezo input a new sound world will open up. Everything is suddenly clear, balanced. I can only recommand that!
I hope my littel excurse was interesting to read and made you want to try music robotics on your own. I can asure you: its a trip to enjoy.I am just about to release my first debut album with help from Mouse On Mars, Kompakt and many many other wonderful people. Its the worlds first techno record made only with robot! You can find it hereIf you want to get updated, please subscribe to our newsletter or follow me on Twitter or instagram.Yours,
Moritz