THE MUSIC INTERACTIVE
http://www.themusicinteractive.com/downloads.html
Downloadable theory games. It takes a bit of time to download, but the programs are free and oftentimes addicting. (I suggest the "Staff Wars" games to kill 10 minutes of X-Wing note blasting!). These are likely supplemental tools to encourage at-home practice rather than the ensemble classroom.
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Recommended games for middle school students: Staff Wars, Rhythm Blocks
Recommended games for high school students: Rhythmic Dictation, Drawn to Keys
THETA MUSIC TRAINER GAMES
http://trainer.thetamusic.com/en/content/music-training-games
Music theory interactive games. Though mainly targeted to the young learner, our middle school students have enjoyed playing some of these games during downtime in advisory or at home.
SOUND INFUSION
http://culturalinfusion.org.au/soundinfusion/
A web based program that allows users to mix, explore, and loop instruments by culture/country.
DON'T WORRY, BE HAPPY
A fun and simple visual and aural game to piece together a cappella arrangements. Based on Bobby McFerrin's "Don't Worry, Be Happy", you can add or delete various vocal lines from that song to get a visual on how a cappella arrangements are created. Nice for vocal classrooms.