Concerts to mark Harrison Birtwistle’s 80th birthday are set to continue to the end of the year. The latest was pianist Nicolas Hodges’ tribute, which included a premiere – a followup to the piece Birtwistle wrote for him two years ago. But where Gigue Machine, the earlier work, is predominantly fast, extrovert and rhythmically propulsive, the new one, Variations from the Golden Mountain, is much more introspective and essentially a slow movement, though one with flashes of virtuoso brilliance.

The title hints at the work’s starting point; the “Golden Mountain” is the Goldberg, and it was from Bach’s monumental set of variations that Birtwistle got the idea of linking a series of short, self-contained episodes into a more substantial musical whole. There’s no apparent thematic link to Bach – even the sense of Birtwistle’s work as a set of variations is hard to discern; if the music’s precipitous changes of mood and manner have any historical antecedents they would seem to be in Beethoven’s late piano sonatas and final set of Bagatelles (Hodges emphasised that connection at the end of his recital by playing one of the Op 126 set as an encore).

The Variations are certainly much more mysterious than the joyous Gigue Machine, with its dogged ostinatos, snatches of curling melody and brilliant keyboard clockworks, which Hodges included later in his programme. He began and ended with the two books of Debussy’s Studies, making light of their technical difficulties, but sometimes presenting them just a bit too assertively, especially in the first book, where clearer, more delicately coloured textures would have been welcome. There was a quirky bit of Busoni, too (his Giga, Bolero e Variazione, which whips some themes from Mozart into a flashy, agreeable bit of froth), which made a suitably unlikely programme companion to the Birtwistle.

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