The original concept for mellow came from founder Patrick Woodcock, a multi-instrumentalist, who had befriended Nicolas Godin (Air) while they were getting their architecture degree in Versailles. They were brought together by their shared passion for 1960s and 1970s vintage instruments, such as the mellotron, the moog, and other old organs and drum machines, which they both subsequently incorporated in their music. After a short stint with Godin during Air's first incarnation, collaborating on Premiers Symptômes as a musician and arranger, as well as on Moon Safari, and co-writing '"Ce Matin-Là"', Woodcock felt he needed to form his own band. He called on his old friend Pierre Bégon-Lours, then a sound engineer who had access to a recording studio near Paris where they recorded their first demos in 1997. Another sound engineer, enlisted by Bégon-Lours, joined the band for a couple of years.

Their first concert took place in Brighton, in 1998. Soon after, they were signed by French independent record label, Atmosphériques. In 1998, mellow joined forces with Air and Sean Lennon for their first French tour.