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“In C” may appear to be about permutations of a C chord, but it’s really about flexibility. No specific instrumentation or performance style is prescribed: Mr. Riley asks only that a pulse be established at the start and run through the performance, and that every musician play, in order, 53 short figures. Matters like the number of times each figure is repeated, and whether (and for how long) musicians pause between them are individual choices. Yet there is meant to be ensemble interaction as well: The work is like a jam session in which the riffs are prescribed but the timing is improvised.

The Darmstadt ensemble, heavily amplified, brought together traditional instruments (two cellos, trombone, saxophone, clarinet, toy piano and xylophone) with a rock band’s backbone (electric guitar, bass and drum kit). Also included were the oldest instrument, the voice, and the newest, the laptop computer. The group’s four laptops were set up so their keyboards’ letters were assigned notes and MIDI timbres, allowing the players — laptopists? — to work through Mr. Riley’s set of figures like everyone else.

Usually the pulse is established by a piano, which holds down the beat with a belllike tone. Here it was the province of an electronic harpsichordlike timbre (presumably from a laptop) and an electric bass, played assertively by Zach Layton and supported by the drummer, David Justh. Mr. Justh added considerable filigree in the course of the 66-minute performance, none sanctioned by the score, but captivating enough to justify its berth.

The singers — Gisburg, Dafna Naftali and Nick Hallett — added a measure of personality that purely instrumental performances of “In C” rarely have and nudged the music in the direction of early Philip Glass. The instrumentalists seemed to respond alternately to the wordless singing and to Mr. Layton’s steadily pummeled bass. Complex rhythms coalesced around that beat, then evaporated as new patterns appeared. And at times, in the most freewheeling sections, the reading evoked the spirit and sound of the Rolling Stones’ quirky “Sing This All Together (See What Happens).”

Supporting the performance, Joshua Goldberg projected computer graphics, based on Mr. Riley’s 53 figures (and others) on a screen behind the ensemble.