Another possibility would be to digitise the carousel music and program
a ROM device, similar to those greeting cards that play a tune.  Whilst
they produce those cards by the zillions, so can afford to use a very
small memory chip and sound unit, there are available other larger,
cheaper, electronic devices, used in electronic doorbells, toys etc.

A fully solid state device should also be more durable than a cassette
unit.  A Google search will probably find a company that can supply and
program a ROM/speaker device.

Colin MacKinnon