NEW YORK, NY.- With a string of No. 1 hits like “Rich Girl, “Maneater” and “She’s Gone” in the 1970s and ’80s, followed by a more recent cultural resurgence, Daryl Hall and John Oates have long been one of pop music’s most celebrated duos.

But over the decades, there have been hints that things were not entirely copacetic between the two men whose names are almost always uttered in sequence. (Oates is the one with the famous mustache.) In the ’80s the group went on hiatus, and both members have at times pursued solo work. In 2020, they announced plans for a 19th studio album, but it never came to fruition; this year, the musicians performed separate tours.

Now, the discord is undeniable as Hall, 77, has filed a lawsuit in Nashville, Tennessee, against Oates, 75, the partner with whom he was inducted into the Rock & Roll Hall of Fame in 2014. Because a judge allowed the complaint to be filed this month under seal, details on the disagreement are scant, but court records classify it as a contract lawsuit.

Lawyers for the two men did not immediately respond to requests for comment.

The lore of Hall and Oates dates back to 1967, when the musicians were students at Temple University. As Oates tells it in his 2017 memoir, both men were performing in separate bands at a sock hop in Philadelphia when gunfire broke out and they ended up in a service elevator together. A few weeks later, Oates’ band split up after two of its members joined the military, and Hall invited Oates to play guitar for his group. Later on, they started writing music together, landing a deal with Atlantic Records in 1972 that propelled them to pop stardom.

“John and I decided when we first came together as kids that we were both going to share the stage,” Hall, who has generally been seen as the principal writer and lead singer of the duo, told Classic Pop Magazine last year. “And that’s really the way that both of us have treated our careers.”

Known for their soulful music and bountiful heads of hair, the duo gained cultural cachet when their music became frequently sampled by hip-hop artists. Though their most recent studio album was a Christmas-themed effort in 2006, new generations have been exposed to their songs through TV and film placements: See Joseph Gordon-Levitt’s elated strut to “You Make My Dreams” in “(500) Days of Summer.”

Hall and Oates have performed together often in recent years, including in a visit to the White House in 2015 and on their band’s most recent tour in 2021. In an interview that year with GQ, Oates said that he and his collaborator had “way more ups than downs,” adding, “It’s actually a miracle, I’m actually shocked that we are able to still play together and it’s great. It’s something that you have to really appreciate.”

This article originally appeared in The New York Times.