Carol, and all who may be interested, in these sites you'll find technical and historical details about bandoneons, and even places to buy one:There is a wide collection of Piazzolla's music in this last site, where you may find tango, but also jazz fusion and pure classical, symphonic works which will surprise you if you didn't have the experience. If you want to hear how the bandoneon makes the violins cry, listen to Lumiere, Nr.1
There are also lots of links to argentinian music. For anyone who likes tango, and have not listened to Piazzolla, I would say that his music is the most advanced wave of the urban folk, growing from its origins and entering the universe of classics while maintaining its roots. Enjoy.
Un abrazo - Andrés