The Billy Strayhorn Music Manuscripts and Estate Papers provide a comprehensive survey of Strayhorn's musical career as a composer and arranger from the early 1930s until his death in 1967. Holograph scores, sketches, parts, and lyric sheets comprise the majority of the Music materials in the collection. These include both original compositions by Strayhorn and his arrangements of works by Duke Ellington and other composers. Strayhorn's holographs are supplemented by small quantities of manuscript materials in the hand of Ellington, scores and lead sheets by other composers, and Walter van de Leur's performance editions of notable Strayhorn works, such as Take the "A" Train , Lush Life , and A Flower is a Lovesome Thing . The collection also contains a significant quantity of unidentified sketch materials, many of which may correspond to items described as 'incomplete' or 'unfinished' in the container list. Scores are paired with corresponding parts, lyric sheets, track lists, and other related items wherever possible.

The activities of the Strayhorn estate, Billy Strayhorn Songs, Inc. (B.S.S.I.), are documented in an expansive series of Business Papers that account for nearly half of all collection materials. These span from the mid-1960s (Strayhorn's will and the establishment of his estate) through 2015 and largely consist of royalty statements and licensing agreements from organizations such as ASCAP, Tempo Music, Music Sales, and Campbell Connelly. Also included is correspondence with Gregory Morris, chief executor of Strayhorn's estate and president of B.S.S.I., copyright renewal forms and databases, organizational documents, miscellaneous subject and project files, and legal materials related to three B.S.S.I. lawsuits filed between 1990 and 2000. The remaining collection materials consist of Scripts related chiefly to Ellington and Strayhorn musicals, Photographs of Strayhorn, Ellington, and other jazz or civil rights figures (Billie Holiday, Lena Horne, Martin Luther King, Jr.), and a variety of Biographical Materials and Miscellany that further document Strayhorn's personal life and musical activities. The latter includes financial documents, contracts, lyric sheets, programs, clippings, several personal effects, and a small quantity of materials related to Fantastic rhythm .