This Eurorack-module (Doepfer A100 compatible) converts a "control voltage" to MIDI.
Compatibility verified with a Yamaha DS55, a Roland RA-30, a Yamaha YPT-230 keyboard and FluidSynth via a M-Audio MIDISPORT 2x2 (connected to a Linux-system).
Using a trimpot you can control the "blackness" of the produced MIDI stream.
This is an example in MP3-format. It is a 10Hz triangle wave played through UTWIN5002 into a MIDI synthesizer (FluidSynth).
Another example. This time a 50Hz triangle wav. And last but not least: 2559Hz triangle wave.
In these examples only the tones were modulated. As stated above, you can also do pitch bending, volume modulating and even resonance tweaking.
This is an example in ".mid-format" (MIDI file on disk). It is the result of two 10Hz triangle waves, one fed to the tone converter and the other to the pitch bender.