It’s a long journey from the masses of Josquin or Palestrina previously offered at St. Bartholomew’s Church’s Summer Festival of Sacred Music to the works of Felix Mendelssohn, so I prepared myself by listening in my mind to Johannes Brahms’s gentle Marienlieder on the subway — a rather synaesthetic experience early on a Sunday morning. The music director at St. Bart’s, William K. Trafka, took a different approach, framing the individual sections of Mendelssohn’s Die Deutsche Liturgie by beginning the program with a thunderous interpretation by organist Paolo Bordignon of Johann Sebastian Bach’s Prelude and Fugue in C minor, BWV 546.

The piece is one of Bach’s most unrelenting, and even shares thematic material with the more famous Toccata and Fugue in D minor, forever associated with the former St. Bart’s music director Leopold Stokowski. The C minor Prelude is a masterpiece of neurasthenic striving, deliciously dissonant chordal combinations, and harmonic “resolutions” that leave the listener ever more unsettled. The fugue is quite severe, the melodic material straining against its tonal bonds, the crabbed nature of its labyrinthine mathematical travels a metaphor for the creation of the universe itself. I thought of Leonard Bernstein’s concept of the pity and power of the world’s greatest music.

Once the magisterial Protestant image was properly framed, the sections of the missa brevis of the composer — properly listed as Mendelssohn-Bartholdy, the Christian iteration of his name — were impressively performed by the church’s choir, or, more accurately, its double choir.Two separate groups were stationed at the front, quickly creating the illusion, as the Gloria section unfolded with a fleshing-out crescendo, that there were many more singers than actually appeared onstage. The opening Kyrie is very quiet, a simple prayer for peace, thus making the following section, which includes the phrase Friede auf Erden (Peace on Earth), seem even more grandiloquent in its relative volume.

Unlike the previous Catholic masses, this work allows its thematic material to travel and grow — not to develop exactly in a musical sense, but rather to strike out on various symphonic peregrinations. The stamp of the 19th century is upon us, and this music must have seemed very daring in a liturgical setting when it was that brash contemporary stuff. Solo voices float in and out and the final “Denn du allein bist heilig” is fugal in nature. All was traversed expertly by the choir, one of the rare jewels in New York’s crown.

At the offertory there was a boon surprise. Mendelssohn wrote extensively in English as well as German, and the choir this day offered a very sweet version of “Blessed are the men who fear him” from his oratorio Elijah. Just as the Rossini Stabat Mater or the Verdi Requiem sound like Italian grand opera, so too this passage from Mendelssohn, transplanted into a church service, sounds remarkably fit and expertly apt. The excerpt is a paean for peace, with gentle leadership in the high tenor voices and a transcendentally beatific crescendo at the phrase “riseth light” that rivals even the nocturne from “A Midsummer Night’s Dream” as the loveliest music in the Mendelssohnian canon. Again, the rendition was superb.

But some things never change, and Mendelssohn demonstrates his grounding in the masses of old by introducing his Sanctus with the cherubic high female voices proclaiming Heilig, heilig, heilig (Holy, holy, holy) just the way that Palestrina or Pergolesi would have done.The program ended with another excerpt from Elijah, “He, watching over Israel” and the Sonata No. 2 for organ.

The lacuna of many modern music critics is their shocking lack of knowledge of religiosity or spirituality. Music like this cannot be totally appreciated without a kindred sense of the faith of its artisans. A musicologist who attempts to write about Bach without grounding in personal faith is reduced to talking about sharps and flats, missing the point entirely.When the subject is Felix Mendelssohn and the interaction of one religion with another, our guide must be secure in his or her own spiritual bona fides. Without religion, this type of musical analysis is as ludicrous as an atheist college professor trying to explicate the works of James Joyce. Sometimes, the soi–disant experts just don’t get it.