CAMBRIDGE — Sacred music doesn’t have to be less complex, less turbulent, than its secular counterpart. In the works of Anton Bruckner, to cite just one example, it’s not easy to separate sacred from secular. The Cantata Singers underlined that point Friday evening at the First Church, Congregational, in “Divining the Incandescent,” a program that included two Bruckner motets, as well as Herbert Howells’s Requiem and Frank Martin’s Mass for Double Choir.

A lifelong Catholic, Bruckner never hesitated to look into the abyss, or take his music there. His “Pange Lingua” (1868) adopts the medieval Phrygian mode, the white keys of the piano starting on E; it doesn’t resolve into E major till the final chord. “Christus Factus Est” (1884), whose first line is “Christ became obedient for us unto death,” becomes disobedient to normal harmonies on the word “obedient,” and the three notes of “death” undergo an improbable, unsettling passage from A-flat major through B-flat minor to C major.