As a Barnard student you can sign up for New York Public Library (NYPL) card! They're free!
The NYPL has more than 6 million items circulating, including books, e-books, audiobooks, music, and movies. Thank you to our friends at the George Bruce branch for working with us to make on-campus card signups happen! The NYPL has 92 locations in Manhattan, the Bronx, and Staten Island. The closest branches to Barnard are the Morningside Heights and George Bruce branches.
While Barnard does have books about music and many videos of musicals/operas, our friends across the street at Columbia's Music & Arts Library (7th floor of Dodge) have a massive collection of books, sheet music/scores, and sound recordings on CD, in addition to a digital music lab. Books and sheet music are lent out for a semester at a time, while recordings are available to be checked out for 4 weeks at a time.
Photo of Gabe M. Wiener Music & Arts Library, courtesy Columbia Libraries
Some of these online encyclopedias and reference sources may be good starting-points for research!