Go to CreatingMusic.com. Decide if you would like to create music, shop in the store or play with music. At the "Create Music" page, your kids can use musical sketch pads to write songs, and the site will play what they've written. You can also play with music at the "Play with Music" page, where you can see how various notes and cords sound.
Go to SFSkids.org and click on the Music Lab. Then click on "Composerizer" to compose music. Add bass lines, melody lines, filler, harmonies and different instruments to songs. Kids can make their own songs and click on the "Play" button for the site to play their music.
Click on Flashmusicgames.com and scroll down the page to find the most popular online flash music games. Kids can choose from Online Piano Game, Online Ear Training, Music Machine or Drums Online. Click on the one you'd like to use, and play. Here you can learn what music sounds like, or create your own sounds and listen to them.