"The only interesting male parts he wrote are both trouser-roles, Octavian, of course, and the Composer in Ariadne"

In opera, a trouser-role (sometimes known as a breeches role, pants role, travesti role, or hosenrolle) is one which requires a male character to be played by a female singer, usually a mezzo-soprano or contralto.

Well-known operatic trouser-roles are Cherubino in Mozart's The Marriage of Figaro, Orpheus in Gluck's Orpheus and Eurydice, Siébel in Gounod's Faust, and Prince Orlofsky in Johann Strauss II's Die Fledermaus.

The two roles mentioned from Richard Strauss operas are Count Octavian Rofrano in the comic opera Der Rosenkavalier ('The Knight of the Rose'), and the composer in Ariadne auf Naxos ('Ariadne on Naxos'), where the trouser-role is taken by a soprano.