These sites for young American children can appear childish in its presentation, but when you read further, you find lots of interesting information that could very well interest even upper intermediate ESL Students.
Play Music presents the instruments, with information about how they are made and the name of the different parts, the artists who used it, and the history of the instrument. You can also listen to the instrument playing. You could use this site to invite music students to present their instrument in English:
http://www.playmusic.org/
The New York Philharmonic Kidzone offers several parts : discover the instruments and make your own; discover the musicians, directors, soloists and composers, with their biography; play in the game zone : go on a scavenger hunt for conductors or musicians, or match the instruments or the composers with the music you hear. A fascinating site for musicians of all age.
http://www.nyphilkids.org/main.phtml