Basic Music Theory: musictheory.net 
Free Online Metronome: https://www.metronomeonline.com/ 

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Metronome

MusicTheory.net
Top Ten TED Talks for Music Education
My Philosophy for a Happy Life - Sam Berns
2009 TMEA Dan Pink Keynote
Karl Paulnack Address
The El Sistema Music Revolution
Center for Music Learning
Music and Emotion Through Time
Music and the Brain - Bobby McFerrin
How to Truly Listen