Here are some external sites that students have found useful for supplementing and enriching their music education.
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musictheory.net
Introductory and intermediate music theory lessons, exercises, ear trainers, and calculators.
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Practice Sight Reading and Sight Singing Exercises Online – Sight Reading Factory®
SightReadingFactory.com makes practicing the important skill of sight reading quick, easy, effective and fun! This cloud-based service allows you to customize and generate unlimited sight reading examples instantly, on-demand for students of all ages and abilities.
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Maryland Music Educators Association
The Maryland Music Educators Association is a leading advocate for music education encompassing a broad range of cultural and musical experiences and the right of every student to experience the power of music. MMEA is a registered 501(c)(3) non-for-profit organization.
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National Association for Music Education (NAfME)
NAfME, among the world’s largest arts education organizations, is the only association that addresses all aspects of music education.