Most of this music is well represented on CD but the rarity is Bernstein’s early Piano Trio. He wrote it when he was a student at Harvard and was being encouraged by the pianist Mildred Spiegel, who knew Bernstein from his teens. Her Madison Trio played the work in 1937 but the composer’s official output starts with the Clarinet Sonata of 1941 42. However, he went back to this Trio and used the March for the Carnegie Hall scene in Act 1 of his musical On the Town seven years later.

After a slow introduction, the fast music has all the hyperactive zest that characterised Bernstein at all periods. The second movement is a comic march opening in simple G major but with a blue note. It soon hots up with obsessive pizzicato passages and an ending in the wrong key. The third movement opens with an almost Debussian Largo before the Allegro winds up with repeated diatonic fragments.

The Copland Sonata gets a thoroughly efficient and rewarding performance from Ehnes and Orion Weiss, and Carter’s early – and uncomplicated – Elegy highlights Richard O’Neill’s mellifluous viola sound. Ives’s Largo for violin, clarinet and piano is a delight and the Barber Quartet confirms the excellence of the Seattle musicians in every way.