British saxophonist Andy Sheppard's third album for ECM marks the next stage in the musical evolution of his Trio Libero, the melody-led freely improvising trio of French bassist Michel Benita and Polar Bear drummer Seb Rochford. But importantly there's a vital new addition in the pioneering soundscaping Norwegian guitarist Eivind Aarset, a contributor to Sheppard's 2009 ECM debut Movements in Colour. More rooted in groove playing and sticking closely to simple harmonic song structures, the quartet improvises with gently subtle brush strokes giving rise to a dreamily shifting, tonally-rich soundscape. Although the recording maintains a serene quality almost from beginning to end, there are also some sublime moments of sonic tension and enigmatic intrigue. Aarset's effects create electronic-like ambient washes of sound and Rochford's percussion purrs beautifully, his sole writing contribution, the quirky ‘They aren't Perfect and Neither am I’ hinting at his assimilation of electronica into his sound. Aside from Sheppard's originals, there's a beautifully tender interpretation of Elvis Costello's lesser-known ‘I Want to Vanish’ and the three parts to their version of Scottish folk song ‘Aoidh Na Dean Cadal Idir’ are perfectly placed as interludes between tracks. That these four musicians are listening and interacting with a close understanding of each other as well as the music they are playing couldn't be clearer. It's a career-defining moment for Sheppard.