Bob Seger, best known for solo hits like "Against the Wind" and "Night Moves," co-wrote Eagles' 1979 chart-topper "Heartache Tonight," a lesser-known but notable crossover between two prolific songwriting camps. The track appeared on Eagles' The Long Run album and became the band's final US No. 1 single before their split in 1980, underlining Seger's uncredited-in-memory but significant contribution to one of the group's biggest hits.

The song was written by Seger alongside Eagles members Glenn Frey and Don Henley, plus veteran songwriter JD Souther, though the collaboration happened by accident during an informal jam between Frey and Seger, close friends at the time. Frey had the verse melody, and Seger spontaneously came up with the chorus line "there's gonna be a heartache tonight," prompting Souther's approval to credit four writers. Country singer Conway Twitty later took his own version of "Heartache Tonight" into the Top 10 in 1983.