Jackson Browne was never an official member of the band, but he played a major role in the early success of the Eagles.

When Browne was a struggling young singer-songwriter in the burgeoning country-rock scene of the early 1970s, he lived downstairs from another young hopeful named Glenn Frey, who had previously worked with J.D. Souther in a duo called Longbranch Pennywhistle and had recently helped found the Eagles. The two became friends and developed a mutual musical admiration, and when Browne was in the studio recording his first solo album, he showed Frey the beginnings of a new song he was working on titled "Take It Easy."

"He asked if I was going to put it on my record and I said it wouldn't be ready in time. He said, 'Well, we'll put it on, we'll do it,' 'cause he liked it," Browne recalled in an interview.

"But it wasn't finished, and he kept after me to finish it, and finally offered to finish it himself. And after a couple of times when I declined to have him finish my song, I said, 'All right.' I finally thought, 'This is ridiculous. Go ahead and finish it. Do it.' And he finished it in spectacular fashion. And, what's more, arranged it in a way that was far superior to what I had written."

"Take It Easy" ended up being the Eagles' debut single from their self-titled debut album. Released in May of 1972, the song, with Frey singing lead, scored the group a No. 12 hit, which they followed up with two more hits from that project, "Witchy Woman" and "Peaceful Easy Feeling." Their debut album was certified platinum after selling more than a million units, launching them on a path that eventually saw the group become one of the most successful in the history of recorded music.

Browne would go on to record his own version of "Take It Easy" for his sophomore album, For Everyman, in 1973. His rendition of the song did not chart when he released it as a single.

Browne and the Eagles would continue to be friends and mutual fans over the ensuing decades. Frey died in January of 2016 at the age of 67 from complications from rheumatoid arthritis, acute ulcerative colitis and pneumonia, and Browne joined the remaining Eagles onstage at the 2016 Grammy Awards that February to perform "Take It Easy" in his honor, with Browne taking over on lead vocals for his longtime friend.

Browne wasn't the only music superstar to play a role in helping the Eagles soar. Don Henley had previously played in a group out of Texas called Shiloh, which Kenny Rogers first discovered in Dallas and brought to Los Angeles to record. Linda Ronstadt subsequently hired Henley, Frey, Bernie Leadon and Randy Meisner to play in her backing band, and they discovered they had so much chemistry together that after playing just one live gig with her, they split off to form their own new band.

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