Covers material published in music and various other fields as they relate to music. Records appear in over a hundred languages. The majority of citations include abstracts. Articles, books, bibliographies, catalogues, conference proceedings, discographies, dissertations, Festschriften, films, and videos are all covered by RILM. Concert reviews, recording notes, and pedagogical manuals if they are of scholarly interest.

Covers all topics related to music, including musical instruments, compositional forms and scientific topics. Biographical entries cover composers, performers and writers. Offers links to related sites including sound archives.

Online collections of sheet music from American history.  Most items are in the public domain, so you can look at the covers (which were often quite colorful) and the music inside.  The collections come from five main collections at Duke University, UCLA, the Library of Congress, Indiana University, and Johns Hopkins.

Developed and maintained by UCSB, this project has digitized thousands of old wax cylinders, all in the public domain and available to download or listen to online.  You can browse or search the collection, I recommend browsing to start, just to get a feel for what they've got.  You'll find minstrel songs, dance music, folk music, opera excerpts, etc.

Another sheet music collection from the John Hay Library at Brown University.

There are all sorts of interesting things to look at here, but in particular check out the online collections of the Aaron Copland Collection, the Bernstein Collection, and the sheet music collections.