Back in the 70s, I was in this club one night where they had and organist and drummer who would accompany guest singers. The organ was a Hammond C3 with a full pedal-board, so the guy was also playing the bass line with his feet. This girl turned up with songs she had written herself and handwritten manuscript which the organist obviously hadn't ever seen or heard before. During the second song I saw him stop playing with his left hand for a bar, and whilst still playing with his feet and right hand he picked up a pencil from the top of the organ, marked something on the manuscript and then carried on without a noticeable break. Afterwards, I went up to him and asked him what it was about. He said that he'd spotted an accidental which wasn't marked, so he'd put it in for her. Now that's what I call sight reading.