On one level, El Loco – released 35 years ago in 1981 – was a continuation of ZZ Top's Texas-steeped blues aesthetic. “Tube Snake Boogie” and “Pearl Necklace,” for instance, stand as the pinnacle of their lip-smacking boogie songs – no small feat. But something else was in play, as a new synth-driven decade dawned.

“This was a really interesting turning point," Billy Gibbons told Music Radar in 2013. "We had befriended somebody who would become an influential associate, a guy named Linden Hudson. He was a gifted songwriter and had production skills that were leading the pack at times. He brought some elements to the forefront that helped reshape what ZZ Top were doing, starting in the studio and eventually to the live stage."

Deep cuts like "Groovy Little Hippie Pad," "Party on the Patio" and even "Heaven, Hell or Houston" – with a synthetic vocal element straight out of The Empire Strikes Back – found ZZ Top charging toward a musical shift highlighted by the glossy, early-MTV smash Eliminator. Gibbons had recently become intrigued by the rising punk, New Wave and synth-pop movements, something hinted at on 1979's Deguello. The closing moments of El Loco made ZZ Top's '80s intentions clear.

"I saw Devo doing a soundcheck at a Houston club – a country and western bar, of all places," Gibbons told Rolling Stone in 2015. "I had heard their first album [1978's Q: Are We Not Men? A: We Are Devo!] and kind of dug it. One of the guys in the band was playing a Minimoog, and he did this [riff] on it. He was just noodling around. But it was enough. What came out of that was 'Groovy Little Hippie Pad' — same figure. It was a direct derivative of punk."

Around the same time, ZZ Top had become fans of the B-52s, specifically "Party Out of Bounds" from 1980's Wild Planet. "Our song 'Party on the Patio' was an extension of that," Gibbons added, noting that music critic "Lester Bangs played it for some punks in New York, and they dug it. It proved we weren't just a boogie band. We had this New Wave edge."

Listen to ZZ Top Perform 'Groovy Little Hippie Pad'

This new melding of styles was encouraged by Hudson, who served as a kind of pre-producer for El Loco – though the album was again officially overseen by Bill Hamm. Hudson helped construct ZZ Top drummer Frank Beard's home studio, and had lived with him for a time. That led to these initial sessions, and then a closer collaboration on 1983's Eliminator.

“Linden had no fear and was eager to experiment in ways that would frighten most bands," Gibbons told Music Radar. "But we followed suit, and the synthesizers started to show up on record. Manufacturers were looking for ways to stimulate sales, and these instruments started appearing on the market."

Elsewhere, ZZ Top downshifted into the purpled emotions of “I Wanna Drive You Home,” which featured a desperately sad guitar figure and an oh-so-lonesome vocal. The blues ballad "Leila" served as lead single from El Loco, followed by "Pearl Necklace" and "Tube Snake Boogie." But none of that necessarily hinted at either the breakout successes to come – or, really, the fizzy experimentation which made this project so different.

Inspired by the new music surrounding him, Gibbons was eager to update ZZ Top's sound. "You think you can get punky? We're gonna get punky!," Gibbons enthused in a 2012 interview with the Guardian. "I knew it was okay because there was no way ZZ Top would lose their blues."

Moments like "Groovy Little Hippie Pad" pointed the way. "Right at the very opening, there it is – the heavy sound of a synthesizer," Gibbons told Music Radar. "For us, there was no turning back."

The Top 100 Albums of the '70s