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Just Intonation Explained
Here is an interesting site explaining how music intonation works with math and fractions. Find out how ratios and fractions denote pitches.
Phil Tulga
Phil Tulga: Fraction Pie Rhythms
Using pies, this interactive site allows you to create your own rhythmic songs. A whole pie equals a whole note, a half pie equals a half note and so on. There are also example songs to listen to.