Since the late 1990s the European Union is planning to get rid of the analog radio signal. It will be replaced by the DAB (digital audio broadcasting) technology. This will be a great opportunity to use the FM band for creative purposes. The Random Appropriation Synth is a project intending to set an example. The instrument receives fm waves and modulates those short soundbits over a keyboard. There is no audio output. Instead there is an fm transmitter. The modulated sounds can be heard over a radio. The initial concept for the modulation interface was inspired by the casio sk-1 lo-fi sampling keyboard.
An early paper prototype showing the different modules and stages of caption, modulation and output of sound:
The FM transmitter turned out to be the trickiest module to build. This video tutorial proved to be the easiest to follow. You will find a more sophisticated version here.
In combination with a hacked voice recorder module we’re almost there.
The final built has no physical modulation interface. Instead of single foot switches (equipped with different resistor values) a single variable photo resistor was added to the hacked voice recorder.
And in order to make things noisier, several voice recorders were connected via a DIY passive mixer.