A musical database was a collection of music.
In 2375, after hearing Kashyk comment on a piece he identified as Mahler's Symphony Number One, Kathryn Janeway commented that he was getting to know her musical database better than she did. (VOY: "Counterpoint")
In 2376, Janeway offered to give the Qomar complete access to USS Voyager's musical database. (VOY: "Virtuoso")