photo credit: "Musical, Theaternacht im Müritzeum" by Thomas Kohler, Creative Commons license
Musical scores and literature about musical theater are intermingled with operas and works on operas.
M 1500: Full score of musicals
M 1503: Piano-vocal scores of musicals
M 1505: Excerpts from musicals (full scores)
M 1507-8: Excerpts from musicals (piano-vocal scores)
ML 50: Libretti / Books
ML 1700-1751: Literature on history and criticism of musicals and of production companies