Composers (See also Music Eras)
- Haydn Society of North America
- Ludwig Van Beethoven: The Magnificent Master
- The Mozart Project
- Music of the Classical Period at the Classical MIDI Connection
- The American Liszt Society
- Centre de Documentation Claude Debussy
- Fryderyk Chopin
- Johannes Brahms WebSource
- Richard Wagner Archive
- Romantics Unbound: Romanticism in Music
- The Schubert Institute (UK)
- The Aaron Copland Collection
- American Popular Music 1900 to 1950
- The ARChive of Contemporary Music
- A Passion for Jazz!
- Rock and Roll Hall of Fame and Museum
- Alexander Technique for Musicians
- Good Ear - Online Ear Training Site
- Guide to Schenkarian Analysis
- Musical Intervals Tutor
- The Orchestra: A User's Manual
- A Practical Guide to Musical Composition
- Ricci Adams' Musictheory.net
- Society for Music Theory
- Solomon's Music Resources
- The Tonal Centre
- American Opera
- The Aria Database
- Lyric Opera of Chicago
- The Metropolitan Opera: Met History
- Operabase
- Opera Glass
- OperadiO
- Opera Today
- Stories of the Operas
- African-American Sheet Music, 1850-1920
- Chopin Early Editions
- Digital Image Archive of Medieval Music (DIAMM)
- Digital Mozart Edition
- E. Azalia Hackley Collection
- Harvard College Library Digital Scores Collection
- Historic American Sheet Music: Rare Book, Manuscript, and Special Collections Library, Duke University
- Lester S. Levy Collection of Sheet Music
- Music for the Nation: American Sheet Music
- Sheet Music Consortium
- Songfile
- UNC-Chapel Hill: 19th Century American Sheet Music Digitization Project
- VARIATIONS Prototype: Online Musical Scores