What’s with all these pianists who can’t seem to play without humming along? Vocalising obviously helps with articulation – and is part of the profound relationship between piano-playing and singing, part of the alchemy whereby a series of hammer-blows on steel strings can be made to sound like bel canto. But humming can be even more than that. ‘When I play, I am making love to the audience,’ said Arthur Rubinstein; well into his 80s the Polish virtuoso maintained an aristocratic composure at the keyboard that excluded any audible manifestation of pleasure. But if pianists, especially more mature ones, start to hum, and if there is an amorous quality to that humming, should we be embarrassed?”