Impromptu(Onyx)**** (4 of 5)The trouble with keeping records is that library science has yet to devise a method of telling you where any piece of music will be just when you really need it. The Schumann piano concerto, for instance. If I look under Schumann, I find two versions. But then there are four more under Grieg – that’s how the record industry likes to pair them up – and heaven knows how many more in box sets of the lifetime works of individual great pianists.Online, it’s no easier, since the same recording will crop up a dozen times under different covers or catalogue numbers and you can waste a whole morning trying to isolate that one half-recollected Clifford Curzon recording of coruscating brilliance. Where the hell is it? (Update: it's under Franck).This is what makes Shai Wosner’s new release so frustrating. A fabulous pianist, incapable of touching an ugly note, Wosner interleaves miniatures of Schubert with matching – at times, surprising – snips by Dvorak, Chopin, Liszt, Beethoven, Gershwin and Charles Ives. I enjoyed the record first time round. I revelled in the connections, especially Ives, on second hearing. But now I am poleaxed by the question of where to put this record once it leaves my desk.Seriously, it’s a problem. How will I ever find ‘Impromptu’ again when I need it to compare with some other release? If you have a solution, do let me know.For the purpose of this review, I very much appreciate what Wosner is doing, drawing out parallel strands of thought between composers of very different character. It is the best background music I have heard all year – like classical radio without the interminable blather, and it makes some mindless chores go faster. Maybe I should use it to start a ‘background music’ category on my groaning shelves? Help me out, here.___Norman Lebrecht has written 12 books about music, the most recent being Why Mahler? He hosts the blog Slipped Disc, writes a monthly essay for Standpoint magazine and is writing two more books.