One Sunday morning this summer, 10 hours or so after her nightclub gig had ended, Tierney Sutton settled into a molded plastic chair on a small, bare stage. She wore reading glasses and no makeup, a departure from her nocturnal elegance as a jazz singer. Even from a six-time Grammy nominee, this particular spotlight called for humility.

The auditorium in Greenwich Village where she sat was named for John Birks Gillespie. That honor paid homage not only to the musical brilliance of the trumpeter better known as Dizzy Gillespie, but also to his lengthy commitment to the Baha’i faith. Ms. Sutton was here to lead a devotional service for several dozen adherents because, for the past 30 years, the double-helix of her own existence has been jazz music and Baha’i religion.

Her collaborator on guitar, Serge Merlaud, struck a bossa nova rhythm, and Ms. Sutton began the standard “Without a Song.” Though the tune can be a jaunty one, she delivered it in a delicate, austere way, as if cradling something fragile. The next song was an original by Mr. Merlaud, a fellow Baha’i, inspired by the faith’s teachings.

So the next hour passed, as the Great American Songbook alternated with jazzy religious odes and a series of readings chosen by Ms. Sutton — some from the Baha’i faith’s 19th-century founder, Baha’u’llah, and others from Albert Einstein and the Rev. Dr. Martin Luther King Jr. All of it formed a whole for Ms. Sutton.