Remarkably little is known about the years Thelonious Monk spent on the road as a teenager, playing organ behind an evangelist and faith healer possibly called the Texas Warhorse. The influence of gospel on Monk’s music — big, strong chords above and a warm, assured spirit coursing below — is evident in everything he wrote. Few contemporary groups tap the same vein as the Como Mamas, a trio of singers from the tiny Mississippi town of Como. On their breakthrough, Get an Understanding, Della Daniels, Ester Mae Smith, and Angela Taylor belted out unaccompanied spirituals with a grit and power that would astonish even the staunchest agnostic. In Durham, too, the trio sings without accompaniment, on a program that considers the thrilling source material of Monk’s distinctive music.