Mark Kinsler, Troy Duncan, and Eli Shahar discussed this topic in
17.07.04 MMDigest.

Removing or replacing a spring in a music box is a dangerous job and
not something to be attempted casually.

If you ever replaced a broken steel tape in a standard tape measure and
had it suddenly spring out of its encasement in all directions at high
speed cutting your hands, arms, and face, then know that the energy of
a wound music box spring is a thousand times that of a measuring tape
and understand the consequences of it getting out of control.

Learn how to do this safely from someone who knows.

Don Shenbarger