A 120V,60Hz Music Box

You fried the AC circuit! It shouldn't take someone who, as North of 60 said, is a "Graduate in Electrical & Electronic Engineering 2009" to figure this out.

Cut the AC cord off where it enters the now 1.5/3/6/9.5/12 volt DC music box and throw it away.

Ask for a refund on your educational expenses, you got cheated.

As Qqberci said, its most probably a problem with the transformer or fuse. If it turns out to be just the transformer, try and identify it better, how many outputs and what voltage they produced.

If you are lucky, its a single output only and it produces (guessing!) say just around 12 volts AC. Then go an buy a 230V ring Halogen lighting transformer which just happens to be around 12 volts....and replace the original transformer with it!

Bigger is better than too small with transformers. An easy way to decide is to buy one that "weighs" about the same or a bit more than the original....not very technical but it should work!! Especially if replacing a "Boxy" type with a ring core, which are slightly more efficient and make less electrical noise (important with audio!). They should also fit in a similar space with a bit of luck!!

This is only good for a transformer with a single output. All bets are off when there are more than one output....sorry.

Hopefully you are then good to go......a little bit of luck will be also needed of course that the components AFTER the transformer were not damaged by the possible over voltage spike.....

A competent person with electricity/electronics should be able to fault find or simply replace the whole power supply with an quality alternative from say ebay.....

I build my own PSs using some great chips and a circuit published in an electronics mag in 2003....of which I have built several versions (different voltages for different people) over the years, which will supply up to 10 amps (at up to 36 volts DC), in a quality right for audio equipment....remember, cheap Power Supplies may let 50-60Hz through to the amp....not good for audio quality!!!

This is not rocket science, none of it and if you are at least little bit mains AC competent easy, if not, leave it alone. Mains can be deathly..... final!