Ralph Vaughn Williams is one of the most significant symphonic composers of the 20th century, and his nine works in the medium compare well with those of Mahler, Sibelius, Shostakovich, or any other composer of the era. Yet he does not seem to have this reputation outside England.

Vaughn Williams consciously endeavored to create a national music as one of his major artistic goals. Although he considered his output tame, his music is incredibly rich and powerful and embodies the English ideal of nostalgia for a period — dubbed “merrie olde England” — that never really existed. Part of that pastoral tradition was the revival of the polyphonic a cappella Mass, no example of which had been composed in England since the time of Tallis and Byrd.

This summer’s Festival of Sacred Music at St. Bartholomew’s Church continued on Sunday as William K. Trafka conducted the double choir and soloists in Vaughn Williams’s groundbreaking Mass in G minor. Written in 1921, the Mass firmly established the liturgical path of the English renascence, with its pacific reaction to the horrors of World War I. If there is a common spawning ground for both Benjamin Britten and Michael Tippett, it is this fervent prayer for peace.

Vaughn Williams had been an artillery officer in both France and Greece. His immediate musical response was the Symphony No. 3, with its moving solo trumpet tribute to his fallen comrades, and this alluring work for the church.

Sunday’s program began with one ofVaughn Williams’s organ pieces, the Prelude to “Rhosymedre,” which ably represented the essential folk element of the pastoral. But as soon as the choir intoned the first notes of the Kyrie, it was apparent that we had entered celestial real estate.

The St. Bart’s choir was especially energetic in the boisterous Gloria, with its lusty intervals that sound for all the world like ultramodernisms. This Mass was written at the same time that Anton Webern was resurrecting the unusual intervals of earlier composers like Heinrich Isaac. During this performance of the Gloria, it was hard not to sit up and take notice of these seemingly discordant sounds. All the rules of Western music that became carved in stone after the William Byrd era are called into question in such a powerful setting. I once knew a music student who called these intervals “demented fifths” because of the combination of augmented and diminished traversals. Especially impressive in this section were the booming bass of Bruce Baumer and the stratospheric upper register of tenor Archie Worley, who could hit those high notes without even a hint of the falsetto.

The ebulliently positive Credo was dominated by the female voices and the fine solos of alto Misa Iwama. Some of the writing may have been a bit ambitious for the sopranos in chorus, and more than a few notes were approximated, but overall this was lovely music-making.

But the most memorable moments of this Mass are in the Sanctus. Vaughn Williams, himself a clergyman’s son, employed the vocalise for an out-of-body experience of the kingdom of heaven. That contemporaneous Symphony No. 3 also uses this wordless singing to explore the ultimate mystery and to attempt to honor the ultimate sacrifice and journey made by the fallen soldiers. (During the service itself, it was extremely moving to hear the offered prayer for the men and women now serving in Iraq who protect us all.)

After the concluding gentle Agnus Dei, with its shimmeringly gorgeous “dona nobis pacem” — possibly the finest music written in England during the last century — the concert came to a close with William Walton’s glorious “Crown Imperial,” sometimes called the “Coronation March.”

The festival itself runs through September and presents a varied selection of Mass settings. Beyond even the spiritual edification, it is fascinating to contemplate how differing composers of various denominations set essentially the same material.A kaleidoscopic variety of religious music — from Josquin des Prez through Mozart and Mendelssohn to 20th-century devotionals from American Jewry (Bernstein and Copland) and French Catholicism (Poulenc and Fauré) — allows regular worshippers and inquisitive guests to contemplate the ecumenical nature of contemporary religion itself. And for those naysayers out there, allow me to point out that the place was packed.

St. Bartholomew’s Summer Festival of Sacred Music continues every Sunday at 11 a.m. until September 17 (Park Avenue and 51st Street, 212-378-0200).