The Kronos Quartet. (Courtesy of the Artists / )

The Kronos Quartet is at it again, committing acts of imaginative generosity in support of creativity. Having commissioned more than 800 new works of music over 40-plus years in action, it now has embarked on a program called Fifty for the Future, a commitment to commission 50 pieces over the next five years, geared to the training of students and young professionals.

Two of these pieces were on display in a Washington Performing Arts-sponsored program at Sixth and I on Saturday — “Hilathi,” by the young Polish composer Aleksander Kosciow, and the world premiere of “From the Book,” by the Dutch-Israeli composer Yotam Haber. Both performances were careful and committed, the quiet, hymn-like simplicity of “Hilathi” handled with warm, balanced restraint and the more extroverted intensity of Haber’s settings of melodies from Jewish liturgy given a lively sense of shape and rhythm and freedom.

These two were flanked by a pair of formidable works that are clearly not student fodder, Franghiz Ali-Zadeh’s three-movement “Mugam Sayagi” and Steve Reich’s “Triple Quartet” — and in both of these, the Kronos had to dig somewhat deeper. “Mugam Sayagi,” an ode to 16th-century Islamic sublimation of sensuality, began in darkness with an extended solo that cellist Sunny Yang floated out weightlessly with a focus that seemed to suspend time. A wild, bubbly dance and a return to a quiet punctuated with gong and drum created a landscape of contrasts, of self-imposed constraints and irrepressible joy.

Reich’s “Triple Quartet” is just that, a piece for three string quartets. It has been performed with 12 musicians onstage but most often, and here (and on the Kronos recording), quartets Nos. 2 and 3 were digital, supplying a great deal of the Bartok-ian rhythmic power while the stage musicians attended to more linear endeavors. This is a powerful piece full of the implications of “triple” — three quartets, three movements and a harmonic structure built on minor thirds — but on Saturday, with the recorded voices going full blast, what the Kronos was doing could barely be heard.

The second half of the program brought a sample of short pieces that have been arranged over the years for the Kronos: an early 20th-century Jewish cantillation that Yang played with uncanny vocal inflection, a highly ornamented Turkish improvisation that violinists David Harrington and John Sherba wove their way though with great delicacy, and three other splendid arrangements of Abel Meeropol’s setting of his anti-racist poem “Strange Fruit,” immortalized by Billie Holiday; a setting for string quartet of Vladi­mir Martynov’s haunting “The Beatitudes” chorus; and finally a rollicking collaboration of the Kronos with the recorded Mexican band Café Tacvba, in an arrangement by Osvaldo Golijov.

The house was packed and appreciative.