If you have a specific article, score or recording you're searching for, Summon is a good place to start. Summon lets you simultaneously search the Library's book collection and many full text journal articles.
IPA Source is the web's largest library of International Phonetic Alphabet (IPA) transcriptions and literal translations of opera arias and art song texts. It currently features over 4311 texts including 685 aria texts.
RILM is a comprehensive music bibliography featuring citations, abstracts, and indexes. RILM Abstracts of Music Literature with Full Text provides researchers with immediate access to a global, multidimensional full-text collection of scholarly music research.
Richard Taruskin’s multi-volume survey of the traditions of Western music wherein the details of music, the chronological sweep of figures, works, and musical ideas, are set within the larger context of world affairs and cultural history.