In an examination of the evident yet overlooked subject of the singing body in opera studies, focusing on the soloist’s voice and role in twentieth-century musical stage works for a single performer offers a number of engaging insights. By observing contemporary staging and practices in light of current performance theories and studies of voice and opera, it is possible to construct an alternative reading of the performer’s embodied voice in musical monodrama, until now not fully addressed in the opera studies discourse. I argue that the performer’s agency should be redefined as a compelling extra-text to be asserted both theoretically and practically in the discourse and production surrounding twentieth-century monodrama and music theater stage works for one performer.