The question of whether two small operas, including one with but a lone singer, could fill the large stage of Glimmerglass Opera has been answered with a resounding yes. If the singers are in peak vocal condition and are equally good actors, that is almost all that is required.
Well, that and the music of master composers. The company serves that up easily with Jules Massenet’s “Le Portrait de Manon” and Francois Poulenc’s “La Voix Humaine.”