This electronic postcard is a touch activated sound synthesizer. When one touches the copper traces of the circuit it is like pressing a button on a keyboard, except in this case the varying electrical resistance provided by ones skin results in varying frequencies being produced. A very light touch produces a high frequency, while a firm pressure results in a low frequency. The sound is output through an onboad speaker or through a 1/8" stereo plug.
Recording Technical Notes:
circuit detail -click for larger image
synthesizer circuit -click to download a sample of music created with this circuit

Steimsiloscratch.mp3 (Synthesizer Postcard Recording)

 
 
1. For this recording I made a slight variation to the synthesizer you see here. I placed a small circle of conductive foam (the kind that integrated circuits are stored in) on top of the lines on the circuit board that are touched to close the contacts and create the sound. The variable resistance of the foam offered slightly more control of the same effect that can be created by varying the pressure of direct finger contact on the same lines.
2. I recorded this track by plugging in the board to the line-in jack on the sound card in my computer. This track was recorded in one take. I processed the track with a "barn silo" impulse in Sonic Foundry's Sound Forge software to enhance the ambiance and create the echo effect.