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 found this transmitter circuit for different frequency ranges in a 1992 documentation. The...
This circuit was found in a French magazine Toute LÉlectronique from 1978. Transistors are not...
This configuration is from a 1964 US documentation valid for any FET. The range of power voltages...