Repertory jazz is often looked upon with scorn. Jazz is about, like, spontaneous improvisation, man. But orchestral jazz works like Birth of the Cool and Africa/Brass are as much about their written arrangements as their solos. Tonight’s recreation of John Coltrane’s Africa/Brass session features Reggie Workman, whose distinctive bass figures begin the original 1961 album. Coltrane wanted a mellow sound to accompany the dense polyrhythms and varied time signatures he, Eric Dolphy, and McCoy Tyner had conceived for Africa/Brass. So Coltrane gathered 10 low brass instruments, as well as a few reeds and a flute, to augment his quartet. The remarkable results are among the saxophonist’s most beautiful achievements. NPR’s JazzSet with Branford Marsalis will be recording for a later broadcast when Workman, a 19-piece band directed by trumpeter Charles Tolliver, and a full gospel choir kick off District Curator’s Jazz Arts ’98 summer festival at 7 p.m. at All Souls Unitarian Church, 16th & Harvard Sts. NW. $15. (202) 783-0360. (Christopher Porter)