We think this is one of the Northern School of Music's annual distribution of awards events. There seems to be a strict uniform of white dresses for the ladies and dark suits for the chaps. It's likely around 1950ish and was taken in Houldsworth Hall where the school conducted all of its larger gatherings.
Houldsworth Hall was at 90 Deansgate (Church House) and was a venue for all sorts of entertainment in Manchester.
Part of the #NSM2020 project "A 20/20 Legacy: the centenary of the Northern School of Music" supported by the National Lottery Heritage Fund.