Not long after the Who's debut album was released, Pete Townshend was already moving on.

My Generation, which arrived at the tail end of 1965, was mostly made up of R&B covers, garage-rock rave-ups and guitar-powered pop that pretty much sounded like every other above-average British rock LP of the period, albeit louder. Their second record, A Quick One, showed a glimpse of Townshend's ambition, wit and skewed sense of what rock music should sound like in the mid-'60s when it arrived in the U.K. on Dec. 3, 1966.

The original songs gave My Generation its heft, and he was ready to branch out from those conventions by 1966. So when the group assembled in a pair of London studios late in the year to lay down tracks for its second album, Townshend – with the other members dutifully along for the ride by contributing their own material – spurred the sessions into daring, and occasionally weird, new territories.

A Quick One is the Who's most delightfully unfocused album, a weaving roll through the band's most democratic period. Bassist John Entwistle contributed two songs (including "Boris the Spider," probably his most endearing composition); drummer Keith Moon did, too (the instrumental "Cobwebs and Strange" encapsulates his boozy, woozy charm in two and a half minutes). Singer Roger Daltrey wrote one song, and there's a cover of the Martha & the Vandellas hit "Heat Wave."

Listen to the Who Perform 'A Quick One, While He's Away'

That left the remaining four tracks to Townshend. By comparison to most of his bandmates' contributions, he sounds rather conventional on three songs, although "So Sad About Us" is one of Townshend's most underrated. But his final number, and the album's closer and de facto title track, dominates the LP and sets up the Who's future and legacy.

Clocking in at more than nine minutes, "A Quick One, While He's Away" distills six separate songs into one cohesive track. It's Townshend's first attempt at a rock opera, prefiguring future classic Who albums like The Who Sell Out, Tommy and Quadrophenia. And it's a masterpiece of tension and release, the story of a woman who has an affair after her boyfriend goes missing, told through various song movements that shift through moods and tempos.

The U.S. release of A Quick One was delayed for six months, when it was retitled Happy Jack and amended with the single of the same name. ("Heat Wave" was pulled to make room for the addition.) The album became the Who's first charting record in the U.S., reaching No. 51; A Quick One made it to No. 4 in the band's native U.K., besting My Generation by one spot.

Today, the album is viewed as the link between the band's more traditional early years and the start of the ambitious period that followed with 1967's The Who Sell Out. Its best moments – like "Boris the Spider" and "A Quick One, While He's Away" – mark a transitional era for the group. It's the moment where the Who broke from the rest of the pack on the way to bigger and bolder projects.

Pete Townshend Albums Ranked

Nothing by the Who. No tribute records to Meher Baba. But we do have concept albums, collaborations and some pretty cool solo records made between band LPs.

Why the Who's Drummer Invited Fans to Moon Him

More From Ultimate Classic Rock