Hi. I remember that when I was a kid, there existed these musical
greeting cards (real ones, not e-cards) -- you opened it up, and there
was a chip inside that triggered and played "Happy Birthday" or some
Christmas song, or something.

1. How do those things work? (what chip do they used, how is it
constructed, etc.)

2. How can I manufacture my own?

3. (barring that) How can I find a place that will custom-build these
for me?

Thanks!

Hi,

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:
http://www.embedded.com/story/OEG20010221S0034

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:

http://kitsrus.com/cob.html

There are many more examples of these using the last search I listed.

Hope this is helpful to you, thank you for writing us.

jessamyn-ga

Google searches used: 

"musical greeting cards" +tune
://www.google.com/search?q=%22musical+greeting+cards%22++tune&btnG=Google+Search&num=30&hl=en&safe=off

"musical greeting cards" +battery
://www.google.com/search?q=battery+%22musical+greeting+cards%22+&num=30&hl=en&safe=off&start=0&sa=N

COB CMOS ://www.google.com/search?num=30&hl=en&safe=off&q=COB+CMOS

fairly good

As for the chip they use .. 

For a very in-depth look I would try and find a copy of Programming
the Motorola M68HC12 Family
http://www.interlog.com/~techart/myfiles/books.html
or on amazon at 
http://www.amazon.com/exec/obidos/ASIN/0929392671/

Or for info on those cards that let you record your own greeting try
looking for info on the ISD1000AP Voice Record & Playback Chip