The concept of "When Twilight Falls," the current program by the Twin Cities-based vocal ensemble Cantus, may seem a bit twee, focusing on that hour as a time for endings and beginnings.

But Thursday night's performance at the Cowles Center in Minneapolis -- the first of five over the next two weeks -- was one of the most deeply affecting concerts I've heard in some time.

There was a quality of melancholy to the individual pieces, organized around such themes as the loss of innocence, death and the afterlife. Even a rousing pirate chantey ended up conveying a sense of mortality.

This was accomplished with the kind of stylistic variety that's come to be expected from Cantus. Whether a 15th-century English carol about the Battle of Agincourt, a William Billings piece reacting to the 1770 Boston Massacre, a Lithuanian folk song or a selection by U2, all provided moments of powerful meditation.

The program featured two world premieres. "Song of Sky and Sea," by Cantus tenor Paul John Rudoi, looked at the approach of death from a lush lyrical perspective. His sensitive setting of text allowed for optimal clarity.

Mohammed Fairouz's "A Source of Light" juxtaposed a letter by Isaac Newton and a poem by 20th-century poet Charles Bukowski. The latter looked at the deaths of many great artists, but with a wit and humor that ultimately proved transcendent.

Cantus sang with its usual clean, crisp sound, creating eerie harmonies that floated across the space. A new shell onstage gave the Cowles Center a warmer acoustic, adding resonance that helped the complex sounds bend.

As usual, the diction was impeccable. Only at moments of the most complex counterpoint was it difficult to understand the words, which is quite an accomplishment.

Each of the nine members had a chance to solo, showing off the individual voices, but it seems wrong to single any one of them out. Even on their own, they always seemed a part of the ensemble.

Intellectually, emotionally and musically rich, this is the kind of program that expands the heart and imparts a richer sense of what it means to be human.