We found this circuit for musical instruments in the March 1992 Radio Electronics magazine. The circuit has outputs according to the desired scale from a crystal oscillator at the indicated frequency.
This circuit for the logic control of the 555 in a power supply was found in the October 1989...
This circuit was obtained from an English magazine from 1979, but can be easily assembled today...
This circuit was found in an old publication and can be adapted for use with modern...