Ursula Oppens continues to champion American piano music. She played Frederic Rzewski’s “The People United Will Never Be Defeated!” during her performance Thursday night. (Christian Steiner)

It is probably safe to say that no single performer has done more for the cause of American piano music than Ursula Oppens. Almost 40 years ago to the day, Oppens walked onstage at the Kennedy Center to play the world premiere of “The People United Will Never Be Defeated!,” a piece she commissioned from American composer and pianist Frederic Rzewski. I wasn’t there on that occasion, but I was in the audience when Oppens played the work for the first time in New York. I came away convinced that I’d heard a fresh, vital contribution to American piano music that would probably acquire a prominent place in the repertory. That it has done.

On Thursday night, Oppens again played Rzewski’s compelling variations, this time at the Clarice Smith Performing Arts Center as part of a series celebrating the 50th anniversary of the International Piano Archives at University of Maryland.

Despite her natural simplicity and modest stage demeanor, there’s something heroic in Oppens’s musical persona. That was evident in her program opener, Beethoven’s Sonata Op. 111. In a performance that spoke more from the heart than the head, the violence that sometimes characterizes this craggy, idiosyncratic late-period masterpiece disappeared and was replaced by an aura of majesty. The second and last movement, a little aria with variations, was spun out with Olympian calm, tempered by gentle but urgent yearning.

Rzewski composed “The People United Will Never Be Defeated!” as a gigantic set of 36 variations on a song once sung by the Chilean supporters of Salvador Allende. Unfolding over about 50 minutes, it explores virtually every resource of the contemporary piano. Far beyond meeting the daunting musical and technical challenges of the score, Oppens revealed the multiple levels from which it derives its unique power and effect. Some variations seethed with revolutionary fervor; others spoke with quiet earnestness; and still others seemed focused on the promise of a better life. There were moments when the hall itself felt almost alive with shifting colors, textures and rhetorical emphases. The ease with which Oppens accomplishes all this stems, on one hand, from the depth of her musicality and, on the other, from the sheer courage of her convictions .

Oppens has commissioned dozens of scores from native composers and not only premiered them but, in many cases, added them to her active repertory and recorded them. She is also an indefatigable and expert educator. But her greatest achievement is surely the eloquence of her piano playing, which exudes warmth, intelligence, contagious enthusiasm, fierce integrity and, to a great degree, the calm that emanates only from wisdom.

Rucker is a freelance writer.