Martin Fröst has already recorded a fine, outgoing version of Mozart’s Concerto in its original form for basset clarinet. A decade on, the opening Allegro has acquired subtler, more reflective shadings. With his smooth, liquid tone, Fröst is always sensitive to the music’s melancholy undertow, bending the pulse in response to a shadowing of the harmony. His discreet added embellishments and inventive ‘lead-ins’ always sound spontaneous. He also vividly exploits the basset clarinet’s added potential for quasi-operatic drama, whether in the first movement’s development or the sportive self-duetting in the finale. The Adagio, not least Fröst’s rarefied pianissimo at the reprise, is supremely eloquent. Other performances using basset clarinet, including Thea King and my own favourite, Wolfgang Meyer, risk a tonal palette that encompasses rawer, more abrasive colours. But Fröst’s poetic and (in the finale) gamesome playing, sympathetically partnered, ranks with the best.

Instead of the usual Clarinet Quintet, Fröst pairs the concerto with the so-called Kegelstatt Trio and a fragment for clarinet quintet completed by Robert Levin. The movement starts promisingly but for some reason Mozart downed tools three bars into the development. Levin’s completion is so elegantly Mozartian that I’d defy anyone listening ‘blind’ to spot the join. The performance is excellent, as is that of the Kegelstatt. Tempi, tricky to judge in this work of moderation, are convincingly chosen. The ultra-refined Leif Ove Andsnes sometimes seems unduly reticent in the opening Andante. But the players relish the operatic interplay of plaintive keyboard, throaty viola and conciliatory clarinet at the heart of the finale. The central Minuet is brisk and brusque. And with the players probing the extremes of pathos and (from viola) fretfulness, its G minor Trio rightly emerges as the emotional crux of the whole work.