I received a tin of popcorn today. Packaged with it was a greeting card. Inside the greeting card was the assembly shown below, which played a song that was loud and clear. The whole thing - tin, three flavors of popcorn, and greeting card - retailed for less than $5. If I wanted to duplicate the music assembly, it would be at least twice as big and I have no idea how much it would cost. Even accounting for economies of scale, that's quite amazing to me.

Of course, the quarter in the picture wasn't included, and there's a story there as well.

 

You can get recordable COB audio players like the one in your card quite inexpensively

 

You or I can order the same thing from China if we pay for a few tens of thousands of them at $2.00 each. They can play any sounds you want.

 

I've seen PIC 10F series chips (6 pin SMD) available in bulk for 10 cents each, they just need a battery and a pushbutton, and will drive a little piezo speaker or magnetic speaker like that one, and obviously can be programmed to play a simple tune.

Actually that might be exactly what is under that black blob on your PCB.