Alien, otherworldly, radiant chords fade in slowly, laced with faint dissonances and staccato punctuations meant to depict unknowable power and the Word spoken by a burning bush. The voice of Moses, transfixed with awe, exclaims, “Singular—eternal—omnipresent—unseeable and unimaginable God!”

This disquietingly beautiful passage of music, the opening of Arnold Schoenberg’s massive opera “Moses und Aron” (“Moses and Aaron”), echoed through the dimly lit sanctuary of Trinity Church in Boston on April 17. The excerpt was one of many that music critic Alex Ross ’90 incorporated into a presentation on 20th-century sacred music. Ross is the music critic for The New Yorker and the author of two books—the Pulitzer Prize finalist “The Rest is Noise: Listening to the Twentieth Century,” a survey of the 20th-century musical tradition, and “Listen to This,” a collection of essays on music. With an extensive playlist of excerpts, he took his audience at Trinity Church through some of the central events and impulses of 20th century religious music.

In his talk, Ross said he was inspired to examine the topic when he was doing research for “The Rest is Noise,” in particular the chapter that focused on French composer Olivier Messiaen. Ross realized, he said, that although the 20th century is usually viewed as the age of secularism, it seems to have produced a more significant corpus of religious music than did the 19th century. This difference, Ross explained in an interview later, is in part explained by the overwhelming social changes the 20th century brought, particularly war and genocide on an unprecedented scale. “Perhaps the strongest factor…[is] the rise of extreme 20th-century violence,” Ross said. In myriad ways, he explained, major composers of the 20th century employed the musical and textual vocabularies of ancient religious tradition in order to negotiate with the realities of the modern world.

For many of these composers, Ross said in his talk, religious texts and the religious musical tradition became powerful means of commentary. “Suddenly you do have a lot of composers who are not devout, who may even be agnostic or atheist in their religious beliefs or lack thereof, nonetheless employing these texts in order to drive home a point of one kind or another. It very often has to do with violence or war,” Ross said in the interview. He pointed to Benjamin Britten’s 1962 “War Requiem,” which uses the text of the traditional Catholic requiem mass in tandem with lines by the British antiwar poet Wilfred Owen. “The text of the Mass is deployed, is reinvented, is confronted with a picture of the modern world…. Britten is ingeniously, brilliantly taking these texts, and in a sense, weaponizing them…deploying them against the violence of the 20th century,” Ross said. He noted the near-howls of “Libera me” (“Deliver me”) and “Dona nobis pacem,” (“Grant us peace”) in Britten’s choruses. “He is making you think about what these words really mean. It is not the ritual that is being recited the same way, week after week in church—it is becoming an almost political utterance.”

The presentation also made note of composers for whom a religious musical vocabulary may have represented an answer to the spiritual destitution of the industrial world as well as the horrors of the century. A number of composers—Ross mentioned Schoenberg, Igor Stravinsky, and Arvo Pärt, among many others—had a more complex relationship with religious faith, in their compositions and their lives, than did composers like Britten, who employed religious texts for more distinctly political effect.

Some of Ross’s subjects had been directly touched by the terrible instances of 20th-century brutality. György Ligeti, most of whose family was murdered in the Nazi genocide, later fled Soviet oppression in his native Hungary to write haunting avant-garde works such as his “Requiem”; Messiaen, whom Ross called “the greatest religious composer since Bach,” wrote his famous “Quatuor pour la fin du temps” (“Quartet for the End of Time”) while interned in a German prisoner-of-war camp in 1941.

Yet, Ross continued, part of what he finds impressive about Messiaen’s piety is the way in which it seems untouched by the ugliness of 20th-century realities. “You can detect a sense of resistance there, in terms of the momentous nature of the piece, against what was going on around him in the war, but in a strange way, I think he would have written the same piece no matter where he was at that time,” Ross said of the “Quartet.” “There’s something kind of eternal and unchanging about Messiaen’s language.”

Messiaen, Ross remarked, drew inspiration from the natural world in some of his religious compositions. “His religiosity is, in a sense, much more everyday,” Ross said. “I think he’s very much focused on these epiphanies that can come upon us—being out in nature, hearing the sounds of birds, looking at the ocean, looking at mountains, and suddenly feeling these deeper, powerful forces at work.”

Ross closed the talk with the final segment of Messiaen’s “Des Canyons aux étoiles” (“From the Canyons to the Stars”), a passage inspired by the majesty of Zion Canyon in Utah. Messiaen’s resounding chords, carrying an almost delirious sense of wonder, filled the sanctuary. “So many people do respond to Messiaen [with an intense emotional connection], no matter what their beliefs, and there is something incredibly powerful that comes to the surface in his music,” Ross said.