when the book is opned, the power to the circuit is connecterd and current is flowing trough the circuit makeing the chip run the music progam
I would think any atmega with some memory could do it - play a simple tune from memory, switch contact to start it off. Little battery to power it, piezo to make the sound. Open one up, bet you find bare die with black gook over it, not even packaged. Cards can be had cheaply at drugstores.
Even if you had those chips in dip you cant do anything