Blondie began to skyrocket to the big time as the '70s drew to a close. They'd first appeared on the scene at New York City's famed CBGB club in 1975, only to be dismissed as a '60s throwback pop group. But Blondie had the last laugh, becoming the most successful act to emerge from that rock 'n' roll underground.

Blondie's 1976 debut offered a fully realized version of what they were all about: equal parts girl-group pop, British Invasion rock 'n' roll, B-movie kitsch and classic sex appeal all rolled into a powerhouse band. The unmistakable focal point was Debbie Harry, who knew her strengths and played them to the max. But the rest of the band provided the solid musical backing she needed to come across.

On 1977's follow-up album, Plastic Letters, Blondie added more aggression to their mix, fine-tuning their style. So by the time they started working on their third album, Parallel Lines, Blondie was ready to start branching out and experimenting with their music. The template they shaped here helped Blondie move out of punk and New Wave genres to a more general pop band.

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Released in September 1978, Parallel Lines was the culmination of everything Blondie had been working toward, both musically and stylistically. It's a modern pop record that nods to the past and looks to the future: The LP begins with a killer cover of the Nerves' "Hanging on the Telephone," followed by their most popular raunchy rocker.

Listen to Blondie’s ‘One Way or Another’

How Blondie Soared to New Levels With 'Parallel Lines'

Blondie completely owned "Hanging on the Telephone," turning it into a power-pop gem. Meanwhile, "One Way or Another" featured one of Harry's best vocal performances, as well as some great guitar riffing. Clem Burke's unstoppable powerhouse drumming guided it all along.

"Picture This" returned to the pure pop form, bursting with a jangly guitar riff. Then Parallel Lines took a left turn with "Fade Away and Radiate," featuring the album's most haunting synth lines, pounding drums and one of Harry's most sultry vocals. King Crimson's Robert Fripp helped set the mood with a guitar line that spins Blondie in a totally new direction. At the end of the song, it drifted into a reggae groove, something the band would later explore in detail.

READ MORE: How Blondie Branched Out After Their Breakthrough

Blondie eventually returned to their pop roots on "Sunday Girl," which was written by guitarist Chris Stein. The song looked back on the great pop songs of the past decade while keeping firmly placed in 1978. And then came the smash hit: "Heart of Glass" actually dated back to 1975, when it was known as "Once I Had a Love" and played at a reggae shuffle. Producer Mike Chapman suggested that the band rework the song as a disco track, and it became Blondie's first No. 1 hit.

This monster song helped propel Parallel Lines to the upper region of the charts, as the album sold a million copies. It remains Blondie's most popular LP, and arguably their best.

Watch Blondie’s Video for ‘Heart of Glass’

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