Like some other early Irma Thomas singles, "Ruler of My Heart" didn't make the national charts, but endures as a relatively well-known classic to serious soul fans in general, and to Louisiana listeners in particular. Thomas is a master of the plaintive ballad, and they don't get much more affecting and melodic than "Ruler of My Heart," written by producer Allen Toussaint under the pseudonym of Naomi Neville. "Ruler of My Heart" starts with a windblown burst of eerie descending female harmonies and a staccato piano trill. The verse, reflecting Toussaint's wide musical schooling, is R&B but more sophisticated musically than most '60s R&B, descending dramatically into a lower key but rising back to the original one so deftly it almost escapes notice. The most memorable part of the song, though, is when the song goes into a more minor mode and gets tenser in the bridge, where Thomas offers a restrained plea to her lover to come back. The backing is impeccable, not too elaborate, but with several satisfying layers, in the high backing harmonies; the almost classically grand piano touches; and the horns that pump away almost subliminally in the bridge. The best part of Thomas's vocal might be the last, when she sensually and wordlessly hums the main melody over the fadeout. "Ruler of My Heart" was reworked, with more bluster and different lyrics, into "Pain in My Heart" by Otis Redding, which became a big R&B hit for him and was covered by the Rolling Stones in the mid-1960s.