When the manuscript of Sir John Tavener’s “Feast of the Immaculate Conception of the Blessed Virgin Mary” reached John Scott, the musical director of St. Thomas, Fifth Avenue, he began to research the instruments right away.

Mr. Tavener, Britain’s most celebrated living composer and an Orthodox Christian, routinely relies on instruments from way beyond the occidental repertory. Included in his new score are items that even the largest orchestra cannot muster: the giant Tam-Tam, Tibetan temple bowls, handbells, the American Indian pow-wow drum, and a Bandir drum.

Having played and conducted many of Mr. Tavener’s works, Mr. Scott was unfazed by the list of strange instruments. He immediately went in search of one he knew least about, the Bandir, a hand-held drum used in Sufi rituals.

Mr. Tavener’s mass, to be given its American premiere at St. Thomas on Friday MAR7, fuses many unlikely instruments, musical styles, and spiritual messages. The mass is entirely sung, not spoken, in Latin, Sanskrit, Arabic, Aramaic, Greek, American Indian, German, and Italian.

Mr. Tavener’s intention is not so much to stress the universality of the mass’s meaning as to represent the glow which surrounds the Virgin Mary, or as Mr. Tavener put it, “to express something of the Divine Effulgence of the Feminine that the Mother of God reveals to us.”

Mr. Tavener is that rare thing, an intellectual composer who believes in God. The son of an organist in a Presbyterian church in Hampstead, London, he fell under the spell of Roman Catholic rituals for a while before converting in 1977 to Eastern Orthodox Christianity. He is a follower of the Swiss universalist philosopher Fritjhof Schuon, who took inspiration from all the world’s great religions.

The oriental spiritual quest Mr. Tavener set out upon has been accompanied by an openness to incorporate exotic musical sounds into his scores. He studied under composers Lennox Berkeley and David Lumsdaine, who introduced him to the music of Pierre Boulez, Olivier Messaien, and György Ligeti, though he also cites Anton Webern as a key influence.

Mr. Tavener, born in 1944, emerged to prominence in Britain during the 1960s, when the world’s music was looted for use in western compositions. In 1968, he befriended John Lennon of the Beatles, who signed him to the Apple label.

But his arrival amid the burgeoning of progressive ideas did not deter Mr. Tavener from religious conservatism. In order to tap into the spirituality he longed for in his music, he preferred to hark back to a time before European classical music emerged, when church music was more simple and, he believed, more spiritual.

“If I wanted to be provocative — and I don’t mind being provocative — I would say the rot sets in with Beethoven. I think Handel is the greatest humanist, and I think humanism should have stopped with Handel,” he said. “What bothers me about Western music is that it doesn’t have an esoteric dimension, in the way the music of the East has, whether it be Byzantine chant, the music of the Sufis, or Hindu music.”

That complexity of approach will be evident on Friday. The music, though surprising and engaging, is easier to understand than the erudite religious notions which underpin it.

“Tavener’s orchestra essentially consists of three separate components: a brass group (4 trumpets, 4 trombones) — often doubled with organ and timpani,” Mr. Scott said. “According to the composer, this represents ‘kingship’ and ‘royalty,’ applicable to Christ. On the other hand, the strings express the ‘femininity’ of Mary. Since the work juxtaposes elements of both Eastern and Western traditions, then the third group of instruments, the percussion, enshrines both traditions.”

If the music offers challenges to the audience, it will also test the abilities of St. Thomas’s choir, in particular its young boy choristers. “Tavener writes for two choirs of voices, divided equally, so each choir consists of four vocal parts — soprano, alto, tenor and bass. The vocal writing is often quite high in the range, and therefore requires great vocal stamina. Tavener’s vocal writing is often quite slow and static too, creating further demands on his singers for breath control,” said Mr. Scott.

“The boys have been learning the work since before Christmas, but I’ve only dipped into it for a few minutes at a time, partly because it is so challenging for young voices,” he said. On Friday the choir will be joined by British soprano Patricia Rozario, for whom Mr. Tavener has composed about 30 works.

The result should be an experience which assaults the senses as much as the intellect, which is Mr. Tavener’s intention. “We can’t go any further with abstraction, with art for art’s sake. If we don’t try to go back to that situation, art will fade out because now it’s just a kind of onanism for music critics and people who like to dissect music. We shouldn’t dissect music; it should dissect us,” he said.