ANONYMOUS 4 | SATURDAY, SEPT. 27, DURHAM Baldwin Auditorium
8 p.m., $10-$42
1336 Campus Dr

Farewell tours are bittersweet, but the vocal ensemble Anonymous 4 has been here before. In 2004, the group tried to move on to other pursuits, but it didn’t stick.

When they visit Durham this weekend, though, it will be their final trip before disbanding during their 2015-2016 season. This “Grace and Glory” tour really is the last call for Anonymous 4. And haven’t they done enough? Since their impromptu formation in 1986, the vocal quartet has sold millions of albums of ethereal medieval music, plus folksong, gospel and shape-note singing. They’ve shared commissions and collaborations with A-list contemporary composers.

While two members of the ensemble are stoking their vocal engines to expand their careers, the other half is switching tracks altogether. Susan Hellauer will devote herself fully to Chant Village, an organization that raises understanding of global sacred music. Jacqueline Horner-Kwiatek is off to Julliard for a doctorate in voice. But Ruth Cunningham and Marsha Genensky are stepping off the stage to practice sound healing and teach music community workshops, respectively.

A final visit to Durham seems paramount for the group. They’ve performed residencies at Duke, and in 2012, they delivered a ballyhooed collaboration with the Mountain Goats in Reynolds Industries Theater. Bespeaking that relationship, their final program is a long love letter to this audience, essentially comprising two albums of material.

Though centuries removed from each other, both sets mix the secular and the sacred. Anonymous 4 begins with the 13th-century Marie et Marion cycle, which describes the virtues of the Virgin Mary and a shepherdess named Marion. In the piece’s final section, sacred and secular texts comingle, the four voices driving them at the same time.

The group closes by revisiting its final album, a compendium of Civil War-era hymns and folk songs. Newly arranged for Anonymous 4, these pieces commemorate not only the 150th anniversary of the war’s end but mark the ensemble’s conclusion, too. Expect tears during the final trio of “Shall We Gather at the River,” “Parting Friends (Farewell, My Friends)” and “Angel Band.” After almost 30 years of holy, relevant music, Anonymous 4 will be missed.