Rufus Jagneaux etched its name in the annals of South Louisiana music with the 1971 hit “Opelousas Sostan,” written by bassist Benny Graeff. Though the joyful, easy-to-sing-along-with tune was its signature hit, Jagneaux was hardly a one-hit wonder. The group was one of the biggest of its day, gigging four to five nights a week and opening for such acts as B.B. King, ZZ Top and Dr. John. It left behind an intriguing body of original work (1971-1975) that is only now available on CD in the form of this bountiful 26-track, two-volume collection.

Like “Sostan,” Rufus incorporated elements of its Southwest Louisiana identity, as evidenced by the southern rock-toned “Sha T Babe,” the wacky “Port Barre” and the harmonica-powered “Quadroon.” Jagneaux even covered Cajun blockbusters such as DL Menard’s “The Back Door,” sung mostly in English and fueled by a psychotic-twangy guitar, and Jimmy C. Newman’s “Lache pas la patate.”

Moreover, this collection shows how Jagneaux evolved exponentially beyond its swampy country-rock baseline into a progressive jazz-rock-funk-soul fusion with arrangements including piano, congas and horns. “(Here to) Carry On” is a prime example of concurrently moving parts: Crosby, Stills & Nash-like vocals, a quick-darting clarinet, hard-rapping congas, Graeff’s fat, funky bass and Dana Breaux’s interleaving guitar lines.

The 6:38-long “Tempted” is even better. A simple rhythm precedes a hard-boppin’ sax and a quirky street-life narrative. Soon there’s a jukin’ jazz jam between sax, guitar, percussion and trumpet before returning to the storyline. It’s a far cry from “Opelousas Sostan” that ignited all of this in the first place.