The first I played was a childrens hymn from the old Methodist Hymnbook - the regular organist let me play just that one when I was about 13. (he died two years later and I succeeded him). It was 'When Mothers of Salem their children brought to Jesus'.
The first hymn I remember singing was in primary Sunday School which used two books (one red, one blue) of childrens hymns by Carey Bonner. 'Jesus bids us shine , with a pure clear light. Like a little candle burning in the night. In this world of darkness, so we must shine. You in your small corner and I in mine'
