London’s Barbican Centre has been famously unpopular with critics and concertgoers ever since it opened, thanks to a monolithic concrete structure and legendarily bad acoustics. But in the last decade, the hall’s managing director has made the absolute best of a bad situation, says Norman Lebrecht. “Today, on the eve of the Barbican’s quarter-century and his own final year, [John] Tusa has completed a £34 million pound refit that has remedied the acoustic, simplified the geography and create physical and intellectual cohesion.”