The death of James Last earlier this year highlighted the often strange relationship between “pop” and “serious” music, Diarmuid Kennedy writes. Last’s weird function seems to have been to take easily digestible popular music and make it even blander – the musical equivalent of a chip milkshake.  Mercifully there are other approaches. David Lang’s version of the Velvet Underground’s ‘Heroin’ makes it an even darker, more haunting song.   The Alarm Will Sound ensemble has knocked out a complete album of Aphex Twin arrangements.   The percussionist Joby Burgess’ Powerplant project has taken on some of Kraftwerk’s canon for their…