They still manufacture kits for making your own musical greeting
cards. The kits come in pieces like the description of the one below:
Melody Card Kit
Kit contains two melody boards with a "Chip on Board" (COB) CMOS LSI
IC. Each has a micro speaker, coin cell and simple leaf switch. These
are similar to those in musical greeting cards. Plays a 128 note tune
that repeats as long as the switch is closed. Speaker and switch can
be removed and relocated.
[source: Debco Electronics, http://www.debco.com/db_online/kit3.htm ].
So, you can either purchase a kit like that one, for $7.95 or assemble
your own with parts you buy yourself. The Embedded.com website has a
detailed discussion on embedded systems in children's toys which
includes a description of how to embed your own system, which can be a
sound system. Read more here:
You can also buy these COB CMOS's directly from people that
manufacture them for use in model train sets, cellular phones and
other purposes, for example:
There are many more examples of these using the last search I listed.
Hope this is helpful to you, thank you for writing us.
Google searches used:
"musical greeting cards" +tune
"musical greeting cards" +battery
COB CMOS ://www.google.com/search?num=30&hl=en&safe=off&q=COB+CMOS