The Eagles launched Glenn Frey to fame, but the singer-songwriter and multi-instrumentalist was already a veteran of the recording studio before he ever helped found the band. Prior to the Eagles, Frey was half of a duo called Longbranch Pennywhistle that released one album — and his duo partner would also go on to play an important role in the

He was a prolific songwriter and musician whose collaborations with the Eagles and Linda Ronstadt helped shape the country-rock sound that took root in Southern California in the 1970s.

Souther was close friends with the Eagles and helped write some of their many hits, including “Heartache Tonight” and “New Kid in Town.”

Souther, who collaborated on some of the Eagles' biggest hits, such as “Best of My Love," “James Dean,” "New Kid in Town," and “Heartache Tonight,” died Tuesday at his home in New Mexico, according to an announcement on his website.

J.D. Souther, a legendary singer and songwriter with roots with the Eagles and Linda Ronstadt, plus later Nashville success, has died at age 78.

Some of his biggest hits included the Eagles’ songs “Best of My Love,” “New Kid in Town,” and “Heartache Tonight.”

Singer-songwriter John David “JD” Souther, known for his collaborations with the Eagles and Linda Ronstadt, has died at 78.