bobby mcferrin plays the audience

Bobby McFerrin builds a pentatonic scale! Neuroscientists! Creating expectation in the human brain! Music Theory! Dancing! You can't go wrong with this one.
music advocacy

This site is about how a musical education affects and benefits your success in life, society and school. It also show how music affects the develpment of intelligence. Thank you, Sam, for finding this one for us!
Kankakee Valley Youth Symphony Orchestra
Students from grades 7-12 can audition for this group, which also offers scholarships for private lessons!
music theory.net

This is the most useful link I know for learning how music works. Use the lessons and trainers to help you improve. Check out the guitar fingering and sheet music pages. It will use all clefs.
blanksheetmusic.net
Here you can customize your own staff paper to read any clef, combination of clefs, key or time signature. This is a very handy site which also includes bass and guitar tabs.
metronomeonline.com
Learn about tempo markings and how to use a metronome, and then use the metronome on this screen.