Voice Lab founder and Southbank artist in residence Mary King opens up the Queen Elizabeth Hall to anyone who wants to sing in this week-long festival. Themes include musical theatre (Mon), pop classics (Tue), world (Wed), gospel (Thur) and jazz (Fri), with a mass sing-off scheduled for Sunday. Designed as a drop-in clinic for the work-weary, King's programme also serves to remind us Londoners that belting out a tune can be a far more effective stress reliever than choking down a couple of mojitos.