Soul Stirrers
A Texas-founded gospel quartet whose musical director R.H. Harris, in the 1940s, broke the ensemble jubilee style wide open — ad-libbing lyrics, singing behind the beat, and introducing a falsetto lead that turned the group's sound from staid harmony into an emotional, preacher-style "hard gospel" lead. That vocal template rippled outward through gospel and the R&B vocal groups (Sam Cooke would later front the group himself) who grew up on their records.
The Soul Stirrers' a cappella harmony style descends from the jubilee-singing tradition that the Fisk Jubilee Singers established when they popularized concert arrangements of the spiritual starting in 1871 — the shared root of every quartet that followed, gospel or secular. Sources name this general lineage rather than a specific direct encounter, so it's the one clearly sourced link, not a fabricated chain.
listen forThe smooth, blended unaccompanied harmony of "Swing Low, Sweet Chariot" is the ancestral sound underneath the Soul Stirrers' own close, unaccompanied harmony on "By and By," recorded four decades later.