CORRECTION:A previous version of this review listed the "Tuscan-Medici" viola as a Guarneri. The instrument is a Stradivari. It also stated that Roberto Diaz is president of the Curtis Conservatory. He is president of the Curtis Institute of Music."

The Curtis Chamber Orchestra dished out a big program for its appearance at the Library of Congress on Saturday, but the main event (and what packed the house) was the world premiere of Jennifer Higdon’s Viola Concerto, commissioned by the library and played by violist Roberto Diaz (now president of the the Curtis Institute of Music and formerly principal violist of the National Symphony Orchestra under Mstislav Rostropovich) on a Stradivari instrument that has been on loan to the library since 1977.

Higdon, who teaches composition at Curtis, produces four or five commissions a year; the viola concerto is the work of a composer who is completely at home in her own idiom. She has internalized an amalgam of jazz, new-age, Americana and classical, avoided the ruminating of the minimalists, and opted for contrast over evolution.

The first of the concerto’s three movements opened with the deepest tones of the viola, exploring a slow melody, built to a martial, high-energy, brass-driven celebration that, having had its say, took a deep breath and calmed to a gentle string fuzz accompanying a sort of solo violin reminiscence.

The urgent second movement drove the viola to technical challenges that Diaz navigated smoothly but without the bowing bite that the music seemed to imply. And the third movement that began with a broad, hymnlike accompaniment to some solo violin and cello interplay, ended in joyous and jazzy rhythmic counterpoint.

In this, the first stop on a six-concert tour, conductor Robert Spano and his conservatory-student forces delivered an incisive and convincing introduction to an appealing piece that deserves to be heard — a lot.

In the shadow of Higdon’s concerto and in another premiere of sorts, the first performance of a newly orchestrated version of Spano’s three “Holderlin Songs” received little advance notice. The soloist, Curtis student soprano Rachel Sterrenberg gave bravely dramatic and richly colored readings of the songs — readings that were often drowned out by those new Wagnerian-proportioned orchestrations that were unleashed in the library’s chamber-sized hall.

Spano led oddly slow, ungraceful and heavy-footed performances of Prokofiev’s Symphony No. 1 in D, the “Classical Symphony,” and the Mozart’s Symphony No. 41 in C, K. 551 (the “Jupiter Symphony”), to open and close the program.

Reinthaler is a freelance writer.