BRATTLEBORO -- Returning home to England in the midst of World War II as both a conscientious objector and an openly gay man, Benjamin Britten must have felt a pariah’s kinship with Christopher Smart.

Though he lived two centuries earlier, Smart, an esteemed poet and writer, was confined to an insane asylum for six years and abandoned by most who knew him. During that time, on scraps of paper smuggled to him, Smart wrote the poem that Britten would later use for his cantata, "Rejoice in the Lamb," a colorful choral work which marries Smart’s text and Britten’s music into colorful, expressive praise and worship of God by all created beings and things.

This weekend, the Brattleboro Concert Choir, under the direction of Susan Dedell, will present Britten’s "Rejoice in the Lamb" and contemporary composer Richard Blackford’s rapturous "Mirror of Perfection" in a program titled "Ecstatic Visions" on Saturday at 7:30 p.m., and Sunday at 3 p.m. at the First Baptist Church, 190 Main St.

The concert features soprano Junko Watanabe, contralto Jennifer Hansen, tenor Marc Winer, baritone Peter Shea, and 10-year-old soprano Elle Jamieson as treble soloist.

Sharing with the Britten a colorful marriage of text and music, Blackford’s "Mirror of Perfection" sets to music little-known poetry by St. Francis of Assisi, written almost as expressive, rapturous love poems to God.

Taken together, the pieces on the program convey effusive, passionate sides of spirituality not often presented in the more familiar texts on which liturgical choral music is based.

"Both St. Francis and Smart are really intent on showing that all creation is equally spiritual. ... It’s in finding the true nature of who we really are that we are really praising God," said Dedell. "These two examples of sacred texts are not, on the surface of it, what the average person thinks of as religious texts."

Scholars feel that Smart (1722-1771) was confined to the insane asylum as much because his father-in-law hated him and for his substantial debts than his supposed religious mania. For much of his confinement, Smart’s only companion was his cat, Jeoffrey, whose virtues Smart extols in the text. Britten chose to compose the voice of Jeoffrey for a child’s voice, which is where Jamieson, most recently heard in local productions of "Amahl and the Night Visitors," comes in.

"I’m very happy to be working with Elle Jamieson on this part," stated Dedell. "She possesses an unselfconscious, natural manner of singing and a beautifully focused purity of sound. I also think her love of animals comes through when she sings about the divine nature of Jeoffrey."

In all, Britten’s "Rejoice in the Lamb" carries that simplicity and innocence with it as it unfolds a profoundly uplifting message.

"In a very simple, almost childlike way, it is filled with ecstatic visions of a world in which all beings move towards perfection and bliss. And this is made more wondrous by the heartbreaking circumstances under which the words were written," stated Dedell.

Another key feature of "Rejoice in the Lamb" is the brilliant organ part, played in this performance by organist Clark Anderson. The organ provides a constant variety of movement and drama, and Anderson is known for an extraordinary sense of tone color.

"Clark loves playing this piece," said Dedell. "This is quintessentially Britten at the top of his game. He knew how to write for the voice very well. My singers are happy as clams."

Blackford’s "Mirror of Perfection" is having its New England premiere with these performances. The piece took London audiences by storm at its world premiere seven years ago. Concert Choir member Susan Bardoun, who had heard the piece, recommended it to Dedell.

"We rightly think of St. Francis of Assisi as a champion of the poor, and a great friend to all creatures," stated Dedell. "But he was also a mystic, subject to a variety of transcendent experiences -- visions, voices, trances -- that resulted in great outpourings of poetry. These love poems to God are highly charged, passionate, even erotic. Blackford’s ‘Mirror of Perfection’ perfectly conveys this overwhelming sense of rapture, longing, and completion."

It is scored for choral, soloists, strings, three horns, harp and percussion.

Tickets for "Ecstatic Visions" are $15 general, $8 for students, and can be purchased by calling the Brattleboro Music Center at 802-257-4523 or by visiting www.bmcvt.org.