The lunchtime crowd lucked into a remarkable treat Thursday at the National Gallery of Art, which offered a free concert featuring world-renowned violinist Christian Tetzlaff in a program of Franco-Belgian violin duos with Antje Weithaas, a fellow German artist. The concert, co-sponsored by the German Embassy and the Embassy Series, bypassed the repertoire of Prokofiev, Bartok and Wieniawski, without which such a program might seem impossible. It featured instead the virtually unknown Sonata in A minor by Eugene Ysaye and duets by Jean-Marie Leclair and Charles-Auguste de Beriot.

The sonata, a massive, almost symphonic work, lacks the creativity and color of Ysaye’s solo sonatas. In a way, the composer’s “freedom” from trying to fill the ear with one unusual solo violin trick or texture after another reveals a paucity of musical invention. The first two movements are prolix and Franck-ian, wandering around too much with too little to do. In the finale, though, the composer reasserts his ability to conjure up unique textures out of the instrument and, delivered with such nimble hands, the work ended strong.

In the earlier, more conventional works, the two artists spun easy, gossamer lines around each other. Intonation was impeccable throughout, other than the difficult, choralelike opening movement of the Leclair.

Although Weithaas has a much less prominent career, her playing matched Tetzlaff’s note for note and was physically more expressive. Tetzlaff, though, clearly had reserves of virtuosity that he barely tapped. Both artists play instruments by the modern German luthier Peter Greiner, but it was fascinating how different they sounded.

Battey is a freelance writer.