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 is the traditional voltage follower configuration with the 741 operational amplifier. The...
S The purpose of this circuit, found in a 1975 publication, is to suppress the noise that occurs when...
In the figure we have the way to trigger a 7555 CMOS monostable with a positive pulse. The time...