Hi,
sorry, but it's just not possible with that type of device.
There is an integrated circuit hidden under the blob of white epoxy; that would have been programmed at the factory & the extra connections needed for that programming are now buried.
It could also have been a one-off programmable or even mask-programmed device, that could not even have had the content changed in the factory.
Even then, it's not possible to program or re-program anything without the full technical information on whatever IC was being used.
You can get various types of recordable devices or sound players that you could possibly use in place of that original device?
How many different pieces of music does it have, and how long are they each (timewise, the dirations)?
ps. Do not try to remove the epoxy covering the IC; it is built using a "COB" type assembly and there are hair-fine connections hidden within that protective blob.
This example has a lot more connections, but the same type of assembly - tiny wires spot-welded between the IC itself and the PCB around it, finally covered with epoxy to prevent anything being damaged: