Although music has an impact on the mind there is little evidence in improves students success overall. However, it certainly does indicate the music does have some benefits in certain situations. Take your pick of the research and go your own study. In the meantime, here are some great sites that not only have music, but show students how it is created and even how to play certain instruments.
Best music link site
Everything here from sing-along songs to camp fire songs, to composing your own. Four pages of links.
Music for teaching
Music, instruments, and more
Great site where students can learn about most aspects of music, play games and create their own pieces.
Lost of lyrics in alphabetical order.
Free kids music in alphabetical order
You can play these songs for your class.
This site has both songs and lyrics from the PBS Store.
A great site for older students. It has folk music instruments, composers from the past, and even games. If you are in the Cincinnati area you can even have your own radio show.
Research about music in the classroom
A survey article on positive effects of music
Harvard Study with mixed results
Article saying it helps students in reading