This passive loudness control was obtained in an old publication. The critical component is the tapped potentiometer that can be adapted with an external resistor network.
This circuit was obtained in a documentation of the 80s, using operational of the time. The...
In the figure we have a third fast adder that we found in an 80's Electronic Engineering. The circuit can...
We found this simple music box circuit that can also be used in a musical bell in a 1991...