The Heilbrun Music and Media Library maintains a collection of bilingual dictionaries for languages frequently encountered by music researchers. Look for them in the Reference section under call numbers beginning with P.
Woodruff Library maintains a large collection of dictionaries for many languages in the Reference Section on the entry level and in the stacks.
Sample catalog searches for dictionaries:
This Subject search: SPANISH LANGUAGE DICTIONARIES—ENGLISH
will find Spanish-English dictionaries.
This Subject search: SPANISH LANGUAGE DICTIONARIES
will find Spanish–Spanish dictionaries.
A general-purpose music dictionary that includes foreign-language terms.
Musical Terminology: A Practical Compendium in Four Languages. Comp. by David L. Boccagna. Stuyvesant, NY: Pendragon, 1999.
Musicmedia Reference ML108 .B55 1999.
Terminorum Musicae Index Septem Linguis Redactus [or] Polyglot Dictionary of Musical Terms. Horst Leuchtmann, ed. in chief. Budapest: Akáemiai Kiadó, 1978.
Musicmedia Reference ML108 .T1
Covers terms in English, German, French, Hungarian, Italian, Russian, and Spanish.
Wörterbuch Musik: Englisch-Deutsch, Deutsch-Englisch [or] Dictionary of Terms in Music: English-German, German-English. Ed. by Horst Leuchtmann. 3d ed. Munich and New York: Saur; Hamden, Conn.: Linnet Books, 1981.
Musicmedia Reference ML108 .W73 1981
Common terms used in German publications and thematic indices
(From the Yale Music Library)
Sourcebook for Research in Music (Crabtree and Foster)
Musicmedia Reference ML113 .C68 2005
German and French word lists (pp. 7-14) translate terms commonly encountered in reference works. The German list includes abbreviations used in Die Musik in Geschichte und Gegenwart.