Rubicon is the first album Mats Eilertsen recorded as a leader for ECM, after appearing as a bassist on a dozen sessions for the label. The Norwegian wrote the music in response to a commission from the Vossajazz Festival, where it was first performed in 2014, and he presents it here with an international septet. It is carefully drawn ensemble writing, mostly low-lit and melodic, in which the group sound matters more than any single soloist.

The reed section pairs Trygve Seim on tenor and soprano saxophones with Eirik Hegdal on soprano and baritone saxophones, clarinet and bass clarinet. Pianist Harmen Fraanje plays piano and Fender Rhodes, and Rob Waring adds vibraphone and marimba, while guitar and drums complete the band with Eilertsen on double bass. After fine-tuning the material on tour, the septet went into Rainbow Studio in Oslo in May 2015. Manfred Eicher produced the session and Jan Erik Kongshaug engineered it.

The opening Canto sets clarinet and soprano saxophone in a slow duet over Eilertsen's quiet arco bass, with a melodic turn that one reviewer heard as close to klezmer. March, at eight minutes one of the two longest pieces, begins with arpeggiated piano. A dark chord from vibraphone and guitar cuts across it, and the piece opens into an extended tenor solo by Seim, supported by guitar, vibraphone and bass. Many tracks use only part of the group. The brief Wood and Water, credited jointly to Hegdal, Waring and Eilertsen, is a hushed exchange between bass, marimba and bass clarinet, and Fraanje contributes the short Cross the Creek.

In The Guardian in 2016, John Fordham described an artist known mainly as Tord Gustavsen's bassist taking a leap to bandleader, with "beautifully crafted music for a septet of contrasting voices". He added that the band "swings with a seductive lightness". Writing for All About Jazz, John Kelman found the album more challenging than Eilertsen's SkyDive Trio and quintet records. Its greatest success, in his view, is that it gives "more complete freedom for the largest cast ever heard on an Eilertsen album" while keeping memorable melodies.

This is the CD edition, ECM 2469, first released on 29 July 2016.