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.
This capacitor for small capacitances is based on the tuning of a receiver circuit. The variable is...
This circuit is from the Motorola LinearDatabook of 1990. It shows how it uses the LF355, 356 and...
We found this circuit in an American publication from 1977. Combining a monostable with a...