Songfacts®:

• This duet is a collaboration with Canadian singer-songwriter JP Saxe, who rose to fame in 2020 with another duet, the Julia Michaels-featuring "If the World Was Ending." Morris and Saxe released the song on January 13, 2021.
• Morris hinted at the collaboration back on September 3, 2020 when she tweeted that she'd been writing with Saxe "all week." "All I've gotta say is DAMN," she added. "He's realllll good."
• Morris and Saxe penned "Line by Line" with help from Morris' "The Bones" co-writer Jimmy Robbins. Saxe told Apple Music's Zane Lowe the song was inspired by a conversation with Morris where they were swapping stories about trying to bottle up feelings in three-minute love songs. "I get to know myself in them, and I think Maren feels similarly." he explained. "The day we wrote 'Line by Line,' we were talking about how sometimes the best feelings are the hardest ones to describe, and how the love we have for our partners seems bigger than what can fit in a song."
  
  "Often, a song can be a really intimate place to fully represent how big love can be," Saxe added. "And I think this song is us making our best attempt."
• The pair croon about how they never get tired of singing of their muses, as there are some things they can only say in a song.
  
  There are things that I sing that I'd never have the confidence to say
  There are things I believe that I only figure out when I sit down to play
  The truth don't scare me in a melody, immortalizing my sincerity
  
  "I have always loved being contemplative of the artist vs. muse relationship in songs," Morris explained. "Writing that day with JP was the most fluid, inspiring session. He's a lyrical faucet. He threw out the line 'immortalizing my sincerity' and it blew my mind. I think, all in all, we wrote the whole song in an hour and immediately recorded it."
• Morris and Saxe were both happily involved in loving relationships when they wrote this song: She married fellow country singer Ryan Hurd in March 2018, and he started dating Julia Michaels after they'd recorded "If the World Was Ending." Morris told Zane Lowe the bond they share with their partners helped them with this tune.
  
  "I definitely think that us both being in love and in relationships with songwriters, it really felt like something that only we could write, at least this way," she said. "And so, I love writing songs about songs, but especially a love song about a song."
• Ryan Marrone produced the song. He's helmed several of Saxe's tracks, including "The Few Things" and "25 In Barcelona."
• Maren Morris and JP Saxe gave the romantic duet its television debut on the March 2, 2021 episode of The Late Late Show With James Corden.
• JP Saxe included the song on his debut album, Dangerous Levels of Introspection.