Kevin Deas headlined “Deep River,” a concert about the spiritual’s evolution into art song that unfortunately illustrated some of what was lost along the way. (Courtesy of Washington Performing Arts )

“Deep River” is one of the most familiar and beloved spirituals in the canon. It was, in fact, the first spiritual to gain widespread popularity — to bridge, in effect, the gap between folk and art song, atop which spirituals as a genre continue precariously to balance. It was recorded in the early 20th century by the (white) violinist Maud Powell, arranged for piano by the (black, British) composer Samuel Coleridge-Taylor, and finally arranged by the doyen of spirituals, Harry Burleigh, a student and amanuensis of composer Antonin Dvorak who was largely responsible for the propagation of spirituals in American concert life, where they have stayed ever since.

This story was at the heart of “Deep River,” a concert Saturday night at the University of the District of Columbia theater that was jointly presented by the PostClassical Ensemble and Washington Performing Arts, part of the latter organization’s season-long exploration of “The Art of the Spiritual.” Unfortunately, beyond the fact that spirituals have undergone a signal but partial transformation into art songs, there wasn’t a lot more to the argument of this particular presentation. Backed up by a “multimedia experience” that involved simply a number of projections and a few audio recordings — including clips of Marian Anderson, Paul Robeson and Burleigh himself — the evening felt at once slender and curiously long, trying to add weight to the concept of spirituals but stripping them of a bit of their enjoyment.

A lot of the heavy lifting was given to Kevin Deas, a redoubtable bass-baritone with a strong but not overly resonant voice who was able to lend a homespun, direct flavor to much of what he sang. He entered alone, singing “Sinner Please Doan Let Dis Harvest Pass,” a less-known song (I wished the evening had offered more of these), and continued with a smorgasbord of everything from a capella (“Swing Low, Sweet Chariot”) to arrangements with piano (Dana Kristina-Joi Morgan played capably) and chorus by Sir Michael Tippett, Augustus Hailstork and others. Anastasia Talley, a soprano with a high voice tinged with metal, took the solo in two numbers, including “Listen to the Lambs,” arranged by Nathaniel Dett.

The chorus, led mainly by Stanley Thurston with crisp understatement and for a couple of numbers by Angel Gil-Ordóñez with colorful gestures, was billed as a combination of the Washington Performing Arts Gospel Choir and the Heritage Signature Chorale; it was a smaller group than that double-billing might seem to indicate, and it sounded a little challenged at times, perhaps due to the amount and range of material it sang. Nonetheless, there were definite highlights, especially a lively arrangement of “Get on Board, Little Children” by Raymond Wise that marvelously evoked a choo-choo train, starting and finishing with a stentorian “get on board” from a solo bass voice in the chorus, and building gradually to full throttle.

There’s a lot to be said about spirituals: their genesis, their evolution, their assimilation and symbolic value in today’s culture. By focusing almost exclusively on their art-song status, Saturday’s concert felt like it missed an opportunity, earnestly applying itself to only part of the picture and falling slightly below the PostClassical Ensemble’s standards for intriguing explorations of repertoire. It was interesting, though, to learn that the Fisk Jubilee Singers, a touring group that did more than any ensemble to popularize spirituals in the late 19th century, offered a version of “Deep River” that was brisk and punchy. To hear the song become slow, moving and emotive was certainly a poignant illustration of what happens when classical traditions get their hands on folk roots.