GERMAN LESSON Lonergan, left, and Pfautsch take it to the keys.

There are actors’ plays, ones that pit diametric traits against each other—intellect clashes with passion, indulgence wrangles discipline, loveably messy takes on obsessively pin-neat—and that give a pair of performers their two-hours, traffic of the stage to display their chops, maybe chew scenery, really work. Marans, though, raises the bar for the “hands” in his two-hander. Though the old odd-couple dynamic pushes Old Wicked Songs through predictable territory, both actors, one portraying a middle-aged, Austrian music professor and the other an arrogant, smirky American pianist in his twenties, must be able to play classical piano. And sing. In German. And do these things not just credibly, but expressively.

Marans’ central conceit is to mirror the growing connection between Stephen (Pfautsch), who’s fled to Vienna to break his creative block, and bombastic but brilliant Professor Mashkan (Lonergan) in a single piece of music (Dichterliebe, a gorgeous, gentle 19th-century song cycle by German Romantic composer Robert Schumann). Songs could be excruciating, but the play, which feels a tad overworked in the metaphor department as well as overlong (the penultimate scene felt, and was applauded, as if it was the end) is at its best a pleasingly simple study of two characters—who seem like honest-to-God real people—realized instinctively and delicately here. This never feels like an also-ran in the actors’ hands, whether they’re playing the piano or off each other.