Leonard Bernstein was an American composer, conductor, writer, lecturer, and pianist. The collection contains correspondence, photographs, writings, personal business papers, the archives from his corporate identity, Amberson Inc., scrapbooks, clippings and press materials, programs, datebooks and schedules, iconography, address books, and fan mail. In addition, it contains music manuscripts for many of his compositions, including The Age of Anxiety (Symphony no. 2); Candide; Chichester Psalms; Fancy Free; Jeremiah (Symphony no. 1); On the Waterfront; Prelude, Fugue and Riffs; Serenade after Plato's "Symposium"; Trouble in Tahiti; West Side Story; and Wonderful Town.

This collection consists of photographs, concert programs, and clippings related to French composer, conductor, and teacher Nadia Boulanger that Harriet Winslow received from 1956 to 1964. Most of the items are signed, dated, and contain simple messages from Boulanger.

José María Castro (1892-1964) was an Argentinean composer, conductor, and cellist. He was a founder and a solo cellist of the Asociación del Profesorado Orquestal chamber orchestra (1928). In 1931 Castro was appointed conductor of the Asociación del Profesorado Orquestal philharmonic orchestra, and two years later he won by competition the conductorship of the Buenos Aires Municipal Band, which he held until 1956. Collection consists of original scores, drafts, orchestral parts, manuscripts, and printed pieces, as well as papers relating to composer's professional career, including correspondence, business papers, photographs, clippings, awards, and posters.

The Robert Craft Collection on Igor Stravinsky consists of music by composer and conductor Igor Stravinsky, primarily scores and parts in the form of publisher proofs, ozalid copies, or other photo reproductions. Most items are annotated by Stravinsky with his corrections, conducting markings, or both. Some parts contain annotations by performers. The bulk of the music dates from the middle of Stravinsky’s neoclassical period in the 1940s and his serial period, which began in the 1950s and continued to the end of his life. Robert Craft became Stravinsky’s music assistant after meeting the composer in 1948. This collection is part of the music and recordings he amassed through their association.

The Aaron Copland Collection consists of published and unpublished music by Copland and other composers, correspondence, writings, biographical material, datebooks, journals, professional papers including legal and financial material, photographs, awards, art work, and books. Of particular interest is the correspondence with Nadia Boulanger, which extent over 50 years, and with his long-time friend, Harold Clurman. Other significant correspondents are Leonard Bernstein, Paul Bowles, Benjamin Britten, Carlos Chávez, David Diamond, Roy Harris, Charles Ives, Claire Reis, Arnold Schoenberg, Roger Sessions, and Virgil Thomson. The photographic collection of Copland's friend and confidant Victor Kraft, a professional photographer, forms part of the collection.

Lukas Foss was an American composer, conductor, pianist, and educator. The collection, which documents his life and career, consists of music holograph manuscript scores and parts, sketches, correspondence, business papers, programs, clippings, promotional materials, contracts, and financial documents.

Andre Kostelanetz was a conductor, arranger, and pianist known for juxtaposing popular and classical repertoire in radio broadcasts and concert performances with some of the world's leading orchestras. He also commissioned several compositions which have since become staples in the orchestral repertoire, including works by Aaron Copland, William Schuman, and Jerome Kern. The collection consists of his musical arrangements, correspondence, business papers, programs, photographs, clippings, and scrapbooks, documenting his 50-plus-year career in the United States. It also includes materials related to the career of Kostelanetz's first wife, soprano Lily Pons.

Serge Koussevitzky was a Russian-born conductor, composer, and double bassist. The archive includes correspondence, personal and business papers, photographs, writings, clippings, scrapbooks, programs, and other materials which serve as a record of Koussevitzky's life and career, and document some of the most significant aspects of twentieth-century music. Through his work as a conductor and publisher, and his efforts to commission new musical works, Koussevitzky maintained deep ties with many of the finest composers and musicians of the day. These figures are represented in their personal and professional affiliations with the conductor. The collection extensively chronicles periods in the history of organizations such as the Boston Symphony Orchestra and the Berkshire Music Center, the Koussevitzky Music Foundation, and the American International Music Fund. Material in the collection dates from Koussevitzky's years in his native Russia and also contains material created after Koussevitzky's death, reflecting his widow Olga's continuing work with various organizations and projects. Musical compositions commissioned by Serge Koussevitzky are part of the Serge Koussevitzky Music Foundation Collection, and are shelved in ML30.3c, ML30.3c2, ML30.3c3, and ML30.3e2.

Artur Rodzinski was born in Spalato, Dalmatia (now Croatia) on January 2, 1892. Rodzinski began as a choral conductor before making his debut as an orchestra conductor in 1920 at the Lwów Opera. In \1925, Leopold Stokowski invited Rodzinski to visit Philadelphia, where he made his debut as a conductor in the United States with the Philadelphia Orchestra on November 15, 1925. In 1926, Rodzinski was a guest conductor of the Philadelphia Orchestra and was later appointed assistant conductor. Rodzenski left Philadelphia to become the director of the Los Angeles Philharmonic Orchestra in 1929. In September 1933, Rodzinski became the conductor of the Cleveland Orchestra for the next ten years, then was music director of the New York Philharmonic from 1942-1947. He also conducted the Chicago Symphony Orchestra, Vienna Philharmonic, Accademia di Santa Cecilia Orchestra, and Teatro alla Scala. The Artur Rodzinski Collection primarily consists of materials related to his conducting career such as correspondence, annotated music, magazine articles, newspaper clippings, legal documents, programs, and advertisements. Most of the collection is in English, with a significant amount of material in Polish.

Max Rudolf was a German-born American conductor and music educator. He is best known for his work with the Metropolitan Opera, the Cincinnati Symphony Orchestra, and the Curtis Institute of Music. The collection contains Rudolf's extensive correspondence with prominent 20th century musical figures, Metropolitan Opera annual files documenting his years with that organization, and a few photographs.

Leopold Stokowski was a British-born conductor and composer perhaps best known for his role as music director of the Philadelphia Orchestra. The Leopold Stokowski Materials consist of manuscript scores for his transcriptions of the works of Johann Sebastian Bach and Modest Mussorgsky, correspondence with prominent composers including Jean Sibelius and Carl Orff, and Arnold Schoenberg’s self-portrait Vision (1910).