Audio compressors often are difficult to learn to operate and requires some technical knowledge about how audio compression works [link] and some training.
Also introducing extra processors in the path of signal is undesirable for some musicians and producers, adducing extra noise, extra distortion
The idea: Take the signal from the audio path only for analisys and envelope generation; and use this envelope to drive a servomotor attached to the gain control of an existent preamp. A pre-attached external potentiometer is an option too.
So, tweaking the controls the user can see how the volume control moves (that's is the didactical part) ; and the extra purist audio user can attach their favorite preamp to the servo.
The attack and release times can't be fast, but would be nice to see while working.
For the vintage audio fundamentalists: use a vacuum tube for the servomotor driver.