Blog - Sketching with Hardware

MidiMassOrgel | The Missing Manual

Published on: | Author: Manuel Hartmann | Categories: 2017a, Projects

This is the missing construction manual and technical documentation for the MidiMassOrgel (MMO).

The MMO is a MIDI instrument we build from March 2th to April 4th during our internship blockwork Sketching with Hardware (2017A). To be precise, it is an organ that uses bottles as pipes, based on the principles of a jug whistle. While blowing gently over the neck of a bottle sounds are produced and different fill levels in the bottle can be used to create different notes.


  • 1x beer crate with 8x beer bottles
  • 1x plywood 4mm (source)
  • 4m PVC-hose 6x9mm (source)
  • 1x slip-on sleeve DN40 (spec sheet, source)
  • 2x socket plugs DN40 (source)
  • 7x toothpicks
  • 7x crown caps
  • 1x Arduino uno (source)
  • 1x MIDI interface (supplied by the lecture)
  • 1x half-size breadboard (source)
  • 7x micro servos (source)
  • 1x 100µF capacitor
  • 1x LED 5mm (source)
  • 1x 220 Ω resistor
  • 1x 5V power plug
  • male/male jumper wires 150mm (source)
  • female/male jumper wires 150mm (source)
  • duct tape
  • double-sided tape
  • masking tape
  • double action hand air pump (source)


  • laser cutter
  • vertical drill press
  • glue gun
  • soldering iron
  • hand saw (japanese saw)
  • cutter
  • scissors
  • and some more


The frame

The MidiMassOrgel repository provides patterns for rebuilding the frame. With this Adobe Illustrator files it is easy to laser cut all the parts of the frame. The patterns have all necessary openings except holes for the hoses.

Constructing the frame was a iterative process:

  1. Building a quick cardboard prototype to check if there is enough space between the bottles to fit the frame and if it’s possible to align the hose so it emits sound (picture 1).
  2. Cutting the basic design with the connection assembly and testing if it fits the beer crate.
  3. Drilling holes for the hoses with a 9mm wood drill. The holes should be 2-3 millimeters above the neck of the bottles and face slightly downward (pictures 3 & 4).
  4. Cutting decorations and openings in the frame.


The AirMuffe

The MMO needs a double action hand air pump to produce the necessary air flow. The main problem is how to distribute the compressed air to the 7 bottles. A first test we made was with 4 hoses taped to the pump hose (picture 1).

The AirMuffe is the crazy simple solution we invented to distribute the air. It is a special pice of drain pipe a “Überschiebmuffe” (slip-on sleeve) that we close on both ends with “Muffenstopfen” (socket plugs); both part are available in every German hardware store. In one plug we drilled 7 holes with 9mm for every bottle one (picture 2, prototype with more holes). In every hole we put a 50cm pice of the PVC-hose and glued them with hot glue. The other plug only needs one big hole to connect with the pump hose. Then we assembled all three parts and the AirMuffe was ready to go (picture 3).

To incorporate the AirMuffe into the organ we fixated it with duct tape and put the hoses through the holes in the frame. We trimmed the hoses to an appropriate length after the installation.

The pipe flaps

We reassembled the pipe flaps from micro servos, toothpicks and crown caps.

  1. Attache the micro servos with double-sided tape to the frame. Place the axis 2-3mm above the bottle necks (assemble the circuitry and run the Arduino sketch once to move the servos to 0 degrees ).
  2. For each bottle:
    1. Put the servo arm on the servo.
    2. Seal the bottle with masking tape.
    3. Place a crown cap on the bottle. A small gap is needed between the hose and the cap.
    4. Use hot glue to first glue a toothpick to the servo arm and then to the cap.

We needed up to three attempts to make it right 🙁



The electronics of the MidiMassOrgel is pretty straight forward. Seven micro servos, one 100µF capacitor, one Arduino UNO, one half-size breadboard, one red LED, one 220 Ω resistor,  one MIDI interface, one 5V power plug and some jumper wires.

We wired it all up and glued it on a piece of plywood (7,5×20,0cm ). The capacitor stabilizes the power supply if all servo motors run at the same time. The LED indicates MIDI input.


The Arduino sketch for the MidiMassOrgel is also located in our GitHub repository. All the source code for MIDI in- and output was provided together with the MIDI interface. We wrote the code to regulate the servo motors. Sometimes cheep servos emit some noise all the time; to fix this problem we disconnect them from the Arduino when they are not triggered. The code snippets below shows how this ist done.

In the openPipe  function the servo gets attached before it is triggered.

// helper function to open pipe
void openPipe(int servoNumber) {
if (servoNumber >= 0 && servoNumber < SERVO_COUNT) {
digitalWrite(LED_PIN, HIGH);
pipeServos[servoNumber].attach(servoNumber + SERVO_START_PIN);
Serial.print("Opening pipe "); Serial.println(servoNumber);
Serial.print("Opening pipe: invalide pipe");

And the servo gets detached in the closePipe function. A little delay in both functions ensures that the servo can do its work.

// helper function to close pipe
void closePipe(int servoNumber) {
if (servoNumber >= 0 && servoNumber < SERVO_COUNT) {
digitalWrite(LED_PIN, LOW);
Serial.print("Closing pipe: "); Serial.println(servoNumber);
else {
Serial.print("Closing pipe: invalide pipe");

Tuning the MMO

Tuning the MidiMassOrgel is quite tricky. There are two parameters that have to be right to get good notes from it.

At first, all the bottles have to be filled with the right amount of water. We tuned in C major with an iPhone App (Cleartune). An empty beer bottle has the note E, so the MMO plays E, F, G, A, B, C, D. We did this step before we installed the electronic and the pipe flaps.

The second parameter is the air flow produced by the hoses. They have to have the right degree and distance to the neck of the bottles. Constant adjusting is the only solution here, to compensate the amount of movable parts and the stiffness of the hoses (custom build valves could be a solution for this problem).

Now your are ready to start our own madness!

linked categories 2017a, Projects


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