Nobody really talks about it much, but the Byrds were one of the '60s' most restless bands. Other groups jumped genres and evolved as the decade wore on, but a lot of these twists and turns were means of survival. For the Byrds, it all came naturally.

They started out as a folk-rock band equally influenced by the Beatles and Bob Dylan. But it didn't take long for other artists outside of the usual pop confines to creep into their music. The Byrds' first two albums -- Mr. Tambourine Man and Turn! Turn! Turn!, both from 1965 -- included expertly played folk-rock songs, an instrumental distinction thanks to Roger McGuinn's 12-string guitar and lots of Dylan covers. By 1966's Fifth Dimension, they were ready to move on.

The album's centerpiece, "Eight Miles High," was inspired by Indian sitar master Ravi Shankar and free-jazz legend John Coltrane, and included a guitar solo that was as close to avant-garde improvisation as mainstream music got in 1966. It tested the waters for the Byrds' next record, Younger Than Yesterday, which was released in February 1967.

Fifth Dimension was the group's first real psychedelic piece, but Younger Than Yesterday is the more accomplished album, a record of wild experimentation that was worlds away from the jingle-jangle rings of "Mr. Tambourine Man." From the backward tapes and raga influences to the horns and, in a sign of things to come, down-home country rhythms that grace a couple of the songs, the album found the band -- working with new producer Gary Usher for the first time -- at its creative peak. The mind-tripping "C.T.A.-102," a song about extraterrestrial life that uses an electronic oscillator to make its point, pretty much sums things up.

All but one of Younger Than Yesterday's 11 songs were written by a band member this time (the lone exception was another Dylan cover, "My Back Pages" this time). Gene Clark, the group's most prolific songwriter, left the band before Fifth Dimension's release, though he did contribute to "Eight Miles High" and a few songs leading up to that LP's sessions.

Bassist Chris Hillman turned out to be the standout writer on the Byrds' fourth album, composing four songs on his own and one with McGuinn, the album-opening single "So You Want to Be a Rock 'n' Roll Star" (which included a trumpet solo by South African musician Hugh Masekela, another sign of the band's burgeoning influences outside of their roots). David Crosby, who was kicked out of the band the next year, also wrote four.

Listen to the Byrds Perform 'Have You Seen Her Face'

The Byrds' move toward country -- which would inch closer with their next album, The Notorious Byrd Brothers, until their full-on embrace of the genre, Sweetheart of the Rodeo -- began here. Hillman, who'd go on to the Flying Burrito Brothers with Gram Parsons, following his one-album gig with the Byrds, was a major architect of their sound moving forward.

His contributions to Younger Than Yesterday -- which was recorded in less than two weeks at the end of 1966 -- helped shape the album and the band's future. He had a hand in the album's two best songs -- "So You Want to Be a Rock 'n' Roll Star" and "Have You Seen Her Face" -- and provided the foundation for what came next. But the Byrds were still a group, even if they were falling apart, and Crosby's jazzier, more challenging entries can't be discounted. It was his growing interest in more worldly music that took the Byrds into more unconventional territory here.

By this time, the band's presence on the charts had waned. After a Top 10 debut album, and two No. 1 singles within six months, Fifth Dimension and Younger Than Yesterday both stalled at No. 24. "Eight Miles High," released just five months after "Turn! Turn! Turn!" hit No. 1, couldn't crack the Top 10. The three singles pulled from Younger Than Yesterday didn't get higher than No. 29; "My Back Pages" would be their last trip to the Top 40.

But they were a more exciting group at this point. And the restlessness that carried them there would take even more turns as the decade wore on, even if Top 40 audiences had mostly given up on them by then. Younger Than Yesterday, like so many Byrds albums from the period, was a transitional milestone that was firmly rooted in its era while simultaneously transcending it.

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