The art-without-boundaries philosophy at the Barnes Foundation found one of endless possible musical counterpoints on Sunday with the Philadelphia Voices performing Vigilia by Einojuhani Rautavaara, the deeply spiritual Finnish composer whose hour-long choral work alone would be a significant event.

This Sunday afternoon program of a cappella choral music, however, was not simply imported from elsewhere, but fashioned specifically for the Barnes' Resounding Voices Choral Series by its co-artistic director Robert Whalen, and hardly stopped there. Just as the Barnes Foundation's art collection is arranged with mixtures of genres and nationalities, movements of the Rautavaara vespers were mixed in with sacred works by forerunners such as Bruckner and Durufle, and contemporaries such as Arvo Part.

At first, I rebelled against the idea. Rautavaara is so seldom heard in these parts, why fuss with this work (written in the 1970s but revised in the 1990s)? But the juxtaposition of composers told you much about Rautavaara's creative path, whose undercurrent of aching dissonance tells you spiritual revelation is not necessary pleasurable.

On the surface, Vigilia is about St. John the Baptist and his fate to baptize Jesus but meet an early, inglorious death. In some performances, Rautavaara would seem to be using the concept as a vehicle, of sorts, for introducing some modernist touches into devotional music. But Whalen's approach was that of a strictly religious work. Musical events were more integrated into each other. Maybe the performance was less exciting than it might be. However, the clarity of the non-church acoustic of the Barnes allowed this more inward approach to be appreciated. Even the bass solos sung by Frank Mitchell benefited from sounding less like a histrionic sermon and more like a heart-to-heart message.

Simply from the standpoint of contour and pacing, the insertion of the non-Rautavaara pieces — Durufle's Ubi Caritas and Biebel's Ave Maria, for example — provided breathing room that you didn't know was needed. Written in a more traditional musical idiom, these works showed just how much the Philadelphia Voices, a relatively new group on the choral scene, deliver expressively molded phrases that can't really be dictated by even the best conductors, but must come from the musical culture of the singers themselves.

In Rautavaara, one might doubt that the Philadelphia Voices could give the right ethnic tang to the music. But the Finnish language gave the choral sound an appropriate edge and even shrillness among the sopranos. One might think that the Crossing has the market cornered on modern-music choral concerts. But programs this thoughtfully conceived and confidently executed are always needed in even the richest of musical communities.