If this doesn’t brighten your Monday, I’m not sure what will. Maybe that says more about me.

The sound comes from a magnetic head moved by stepper motor. To make a specific sound, head must be moved with appropriate frequency…

To move the head you need to activate the drive by pulling the DRVSB0 or 1 (depends on the cable you have and the connector - notice the crossover on the FDD ribbon cable) pin low and then falling edge on STEP pin makes the head move one step in direction dependent on DIR pin state.

An ATMega microcontroller is generating those frequencies and it makes the drives play music. #source