Open Theremin V3 with MIDI interface control software for Arduino UNO

Based on Arduino UNO Software for the Open.Theremin version 3.0 Copyright (C) 2010-2016 by Urs Gaudenz https://github.com/GaudiLabs/OpenTheremin_V3

Urs makes also a very clear presentation of this MIDI feature on his website (many thanks !): http://www.gaudi.ch/OpenTheremin/index.php?option=com_content&view=article&id=200&Itemid=121

Don't click on the files!

Click on the "Download ZIP" Button to the right or Click here Then unpack the archive.

Open Source Theremin based on the Arduino Platform

Open.Theremin is an arduino shield to build the legendary music instrument invented by Leon Theremin back in 1920. The theremin is played with two antennas, one to control the pitch and one for volume. The electronic shield with two ports to connect those antennas comprises two heterodyne oscillators to measure the distance of the hand to the antenna when playing the instrument. The resulting signal is fed into the arduino. After linearization and filtering the arduino generates the instruments sound that is then played through a high quality digital analog audio converter on the board. The characteristics of the sound can be determined by a wave table on the arduino.

For more info on the open source project and on availability of ready made shield see:

http://www.gaudi.ch/OpenTheremin/

Installation

1. Open up the Arduino IDE

2. Open the File "Open_Theremin_V3.ino"

3. In "Application.cpp", take care of selecting MIDI mode that correponds to your cituation (put "//" in front off inadequate line - MIDI through serial is selected by default here):

   Serial.begin(115200); // Baudrate for midi to serial. Use a serial to midi router http://projectgus.github.com/hairless-midiserial/

   //Serial.begin(31250); // Baudrate for real midi. Use din connection https://www.arduino.cc/en/Tutorial/Midi or HIDUINO https://github.com/ddiakopoulos/hiduino

   I tested "Hiduino" and "midi to serial" modes, both are OK.

4. Selecting the correct usb port on Tools -> Serial Port

5. Select the correct arduino board from Tools -> Board

6. Upload the code by clicking on the upload button.

Added and removed compare to Open Theremin V3.

Serial communication implemented for program monitoring purpose was removed (Particularly during calibration). If you need to monitor calibration for antenna problem fixing, please use original master branch from https://github.com/GaudiLabs/OpenTheremin_V3.

Serial port is used to send midi messages now.

How does it works ?

PITCH : It uses first note detected at volume rise to generate a NOTEON. Then it uses PITCHBEND to reach pitch as long as pitch bend range will do. Beyond it generates a new NOTEON followed by a NOTEOFF for the previous note (legato). Pitch bend range can be configured (1, 2, 7, 12 or 24 semitones) to align with synth's maximum capabilities. One exception is that I desactivated pitch bend in 1 semitone mode because portamento does a better job then.

VOLUME: It generates VOLUME continuous controler, starting NOTEON and ending NOTE OFF (when playing staccato). The trigger volume can be configured so as we have some volume at note attack on percussive sounds.

CONFIGURATION: There is two calibration mode:

1. If REGISTER POT turned counter clockwise at entering in calibration mode -> Runs normal calibration of antennas.

2. If REGISTER POT turned clockwise at entering in calibration mode -> Records midi settings as per pot position BEFORE entering in calibration mode:

   VOLUME POT : sets volume trigger level
   
   PITCH POT : sets pitch bend range (1, 2, 7, 12 or 24 semitones) 
   Use exactly same pitch bend range on your synth. Maximum setting possible is recomended. 
   
   TIMBRE POT : sets Channel. In the absence of graduation, timbre variation may help 
          (Wave Form 1 low = CH1, WF 1 High = CH2, WF 2 Low = CH3, etc...)
   

MUTE BUTTON: Sends ALL NOTE OFF on selected channel and stay in mute until it's pushed again.

AUDIO: Audio processing from antennas to output jack, including pots, LEDs and button functions, is exactly the same as in open theremin V3.

What can I do to get a theremin like glissando?

Set pitch bend range of the theremin with a high value (12 semitones or 24 semitones).

Set pitch bend range of the synth with the same value

Closest to real theremin settings (pitch bend range = 24 semitones):

1. Set pots like this: Volume = Min, Pitch = Max, Register = Max, Timbre = Midi channel.

2. Push button for two seconds.

3. Then set pots as for audio (Example : Volume = Mid, Pitch = Mid, Register = Wanted octave, Timbre = any)

4. Play (you can mix synth and audio if you want)

If I do not trigger with the volume hand it also seems to trigger a new tone with the pitch antenna. Guess this is how MIDI works.

Yes, with settings above, if you trigger a note (with volume loop) and go in one direction (with pitch antenna) a new note will be triggered after two octaves.

This is a limitation of midi. Maybe some synth can perform pitch bend on more that 2 octaves but none of mine does...

Tweak

In the following lines of application.cpp:

  // Set key follow so as next played note will be at limit of pitch bend range
  midi_key_follow = (double)(midi_bend_range) - 0.2;

The "-0.2" could be changed into another value from "0" to "-0.5" depending on how good you are to reach center of the note that you play. "0" is for very good players. "-0.5" is very permissive and generates note toggling in 1 semitone mode. "-0.2" is the limit where my favourite chromatic tuner's green LED turns off (and it is OK for me).

LICENSE

Original project written by Urs Gaudenz, GaudiLabs, 2016 GNU license. This Project inherits this 2016 GNU License.

Check LICENSE file for more information

All text above must be included in any redistribution