The frequency of each note depends on R2, which must be replaced by a keyboard. The circuit is from Radio Electronics from April 1980. The power supply is 9 V for the amplifier used.
We obtained this circuit from an old Argentine magazine. The circuit originally uses germanium...
We found this circuit in an old English publication. The sensor is a common LDR. and the...
This circuit is from an 80's component manual. The components are from the time, but the circuit...