The Cornell University Library homepage features a single search that includes the library catalog, articles, databases, and more.
These can be searched separately or simultaneously.
To discover articles (that is, to find citations for articles that you don't yet know about), use the music-specific databases listed below, especially Oxford Music Online, RILM Abstracts of Music Literature, and Music Index Online.
Many individual journals are available electronically, usually from ca. 1996 to the present. You can search by title in the catalog, or use the "E-journal Titles" tab on the Cornell University Library homepage.