IMSLP/Petrucci Music Library
Free sheet music downloads of major repertoire

Hyperion Records
Extensive programme notes

Classical.net
Good general reference site for composer biographies, repertoire and much more

Allmusic.com
Good general reference for music history, genre focus, biographies, etc.  Also good blog.

Dolmetsch Online
Good Musical dictionary, theory tutorials, history reference and information about the physics of music

TonalityGuide.com
Comprehensive harmony and analysis tutorials with sound files and musical examples

Virginia Tech Multimedia Dictionary
Multimedia musical dictionary, each definition is supported by audio files.

CHICO Instrument Encyclopedia
Instruments from around the world expained with sound clips.

Essentials of Music
Glossary with audio clips

Naxos Glossary of Classical Music
Glossary and links to other information about Classical Music to support their recorded catalogue

Opera Resource
complete resource on the web for opera music, books, links and information

Glossary of Musical Terms
Simple Glossary

Cadenza.org Glossary
English, French, German, Italian or Serbian Musical Glossary

Online Music Dictionary
Free dictionary of musical terms

Classical Almanac
Every significant date in Classical Music History

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