The 1992 Rieger organ in St Giles Cathedral, Edinburgh : one of the venues for the postponed IAO Festival  (see below) 'I don't envisage, even up to the end of the year, we will be back to our normal services,' said Sarah Mullally, the Bishop of London, a few days ago, referring to the current lockdown on UK churches.  So it may seem slightly perverse to be looking at performance skills in this week's Learning during Lockdown, when the world is currently preventing most organists from performing at all.  But lockdown is possibly an opportunity to…