Koerner returned to Minnesota and became involved in the Minneapolis music scene, where he met
Dave Ray and
Tony Glover. They formed a loose-knit trio, releasing albums under the name
Koerner, Ray & Glover. In a 1964 interview in
Melody Maker,
John Lennon called the record one of his personal favorites. In 2016,
David Bowie told
Vanity Fair that the album introduced him to the sound of a 12-string guitar, and praised it for "demolishing the puny vocalizations of 'folk' trios like the
Kingston Trio and
Peter, Paul and Whatsit, Koerner and company showed how it should be done." Koerner was the first musician that Dylan met in Minneapolis, at the Ten O'Clock Scholar coffeehouse. Dylan wrote in
Chronicles that "Koerner was tall and thin with a look of perpetual amusement on his face. We hit it off right away." Koerner was a few years more experienced as a musician, and took Dylan under his wing to teach him folk and blues songs. "When he spoke he was soft-spoken, but when he sang he became a field holler shouter. Koerner was an exciting singer, and we began playing a lot together", Dylan wrote. They performed often as a duo, but each also played frequently on his own. Around this time, Koerner also met Tennessee bluesman
Big Joe Williams, whose modified nine-string guitar inspired Koerner to try similar modifications to his own instrument, including adding a seventh string so that he had two "G" strings an octave apart. (One song, "I Ain't Blue", was later covered by
Bonnie Raitt on her
debut album.) The duo split up in the early 1970s. Koerner pursued an unsuccessful career in filmmaking, retiring from music and moving to
Copenhagen, Denmark, where he made the black-and-white film
The Secret of Sleep. After more than a decade, he released a new album, ''
Nobody Knows the Trouble I've Been, on Red House Records in 1986. In 1990, Red House released a live album recorded at the World Theater in St. Paul, Legends of Folk'', featuring Koerner with
Ramblin' Jack Elliott and
U. Utah Phillips, which Richard Meyer of
Allmusic called an "excellent concert recording." and with Glover on the concert album
Live @ The 400 Bar in 2009. A retrospective album capturing a solo live performance and radio interview recorded on the same day as a studio session for
Blues, Rags and Hollers,
March 1963, was released in 2010. The album was released by Mark Trehus, owner of the Minneapolis record store Treehouse Records and a longtime fan of Koerner, on his label Nero's Neptune Records, along with a re-release of
Music Is Just a Bunch of Notes which included a video of Koerner's experimental film
The Secret of Sleep. Koerner performed at the
Newport Folk Festival in Rhode Island in 2012. He played "retirement" shows at the
Cedar Cultural Center in 2017 and 2019. When he officially retired in 2023, Koerner donated one of his guitars, a 12-string
Epiphone, to Palmer's, where it was placed on display in a glass case. Koerner also gave his 12-string
Gretsch guitar to his friend
Charlie Parr, a fellow blues musician, requesting that Parr continue using it on stage. In a profile on Koerner for the magazine
Record Collector in 2013, the musician discussed his relative lack of fame compared to musicians like Dylan and Raitt who came after him: "I think you have to really want that kind of success and adulation. And I'm just not like that. ... It's just not in my character to go chasing after fame." ==Legacy==