The 20-year-old group Eighth Blackbird, in its latest incarnation, offered dazzling performances at the Kennedy Center — but not such dazzling music. (Saverio Truglia/Saverio Truglia)

How far new music has come. A couple of decades ago, a new-music concert at the Kennedy Center probably would have ­focused on academic music. These days, alt-classical or indie-classical is the dominant strain. The new-music sextet Eighth Blackbird has managed to keep a foot in both worlds, but its concert Monday night at the Kennedy Center was definitely on the indie side of the spectrum.

If only the music had been better. In the company of talented and facile 30-something composers — David T. Little, Ted Hearne and Bryce Dessner — David Lang, once himself an enfant terrible in the vanguard of alt-classical music and now a Pulitzer Prize-winning elder statesman, sounded like a master of gravitas and profundity.

Eighth Blackbird has come a long way, too; the group has attained elder-statesman status itself, and it is celebrating its 20th anniversary. Like many 20-year-olds, the ensemble has moved past its coltish, awkward years into hip assurance. It has had two personnel changes: Yvonne Lam, a former assistant concertmaster with the Kennedy Center Opera house orchestra, joined in 2011, and Nathalie Joachim, an edgy multi-genre performance artist who has long been pushing boundaries with her flute, is new this year.

Joachim’s approach meshes well with Eighth Blackbird’s theatrical streak; the group tends to offer dramatic stagings, “evenings” as opposed to concerts. On Monday, the stage of the Terrace Theater was crowded with stuff — ladders, hanging fabric, a couple of stopped clocks and some naked light bulbs, in addition to the battery of instruments and music stands — that provided a convivial evocative junk-shop atmosphere for a program focused on memories of the dead. The purpose of the stuff, it turned out, was simply to provide atmosphere, although Joachim partly climbed a ladder at one point.

But this particular program didn’t offer these gifted musicians a lot of meat into which to sink their teeth. The marquee event was the world premiere of Little’s “Ghostlight,” commissioned by the Kennedy Center’s Abe Fortas Memorial Fund. Little is a star of the alt-classical scene; his ­opera “Dog Days” has won near-universal acclaim, and his next opera, “JFK,” will have its premiere in Fort Worth in April. But “Ghostlight,” to my ear, lacked substance. Each of its four movements is dedicated to a deceased artist, and there was certainly contrast, from the intense second movement (for the painter Remedios Varo), with its fierce extended chords and drum booms repeating and repeating, to the lyrical and delicate finale (for the composer Lou Harrison), with singing solo lines of violin and flute. But it never managed to convey much beyond blunt approximations.

Ted Hearne’s “By-by Huey” tackled a contemporary subject — it’s based on a Robert Arneson painting of the man who killed activist Huey P. Newton — with a lot of impassioned variety of sound. And Dessner’s “Murder Ballads,” which concluded the program, engagingly revisited early folk songs. Which was all fine, as far as it went, but it didn’t make the evening as substantial as it appeared on paper. It was left to Lang’s three small works from his cycle “Memory Pieces,” evocations of friends who had died, beautifully arranged by the group’s cellist, Nicholas Photinos, and pianist, Lisa Kaplan, to bring across, with a light touch, the poignancy and profundity of their subject.