The Morgan Library & Museum houses one of the finest collections of music manuscripts in the country. In addition to a large collection of musicians' letters and first editions of scores and librettos, it has the world's largest collection of Mahler manuscripts and substantial holdings of Brahms, Chopin, Debussy, Mozart, Schubert, and Richard Strauss. The collection of forty thousand items spans six centuries and many countries. It includes over eleven hundred music manuscripts, twelve thousand rare printed scores, seven thousand musicians’ letters, thousands of librettos, playbills, and portraits. The Morgan's holdings of material relating to the lives and works of the dramatist William S. Gilbert and the composer Arthur S. Sullivan form the most extensive archive of its kind in the world.
Although Pierpont Morgan is not on record as evincing any notable interest in music, he did make two important purchases: the two earliest dated letters of the thirteen-year-old Wolfgang Amadeus Mozart and the manuscript of Ludwig van Beethoven's Violin Sonata no. 10, op. 96, in G Major.
The Morgan's music collection is the result of the generosity of several donors and lenders. In 1962 the Dannie and Hettie Heineman Collection, a small but exceedingly well-chosen selection of music manuscripts, was placed on deposit and then formally given to the Morgan in 1977. In 1968 the institution became a major repository of music manuscripts with the donation of Mary Flagler Cary's extraordinary collection of manuscripts, letters, and printed scores. In 1972 Robert Owen Lehman put on deposit his collection of manuscript scores, the greatest private collection of its kind. In 2008 the Morgan acquired the James Fuld Collection, by all accounts the finest private collection of printed music in the world.