The San Francisco Symphony has developed an interactive site for young-middle school students on music, instruments, and composing. On SFS Kids students can learn to compose and play music. It is a free site and does not require any log-in for your students.
There are lots of sections to click on and just dive into -
To start it's probably a good idea to start with the "Discover" section and see how the site works.
Most computer-savvy kids will follow along quite easily. In this section they listen to samples of different styles of music performed by the symphony orchestra. Dialog boxes pop up giving information about the style of the piece that they are hearing. After listening to recordings, students can then go to a game section where they are to recognize and match rhythms.
I've played around with it for a short time and was impressed with how much information is contained in the site as well as how students can compose a variety of pieces within a short time.
SFSKids Definitely worth checking into!!
For some further info click HERE.