At the BBC Proms this year, an Icelandic pianist dressed like a Wall Street broker played a slow movement from a Bach organ sonata that had the audience first gasping and then stamping their feet. This was an encore to a performance of the Schumann Piano Concerto that neither milked the poetry nor romped thrillingly through the finale – and that, too, nearly had the Prommers throwing their underwear at the shy soloist.