Russ, I agree with the studio sessions, however, I don't have worry about that part of the business - never did.
Most of the readers I know personally, many of whom are excellent readers, cannot play a note without having the dots in front of them. Additionally, they playing is often very stilted and regimented sounding - there was no emotion or feeling whatsoever in their performance. Audiences pick this up instantly, IMO.
The vast majority of the entertainers I've come across during the past 60 years never had a piece of sheet music in front of them while performing on stage. They never had to think twice about any song someone requested, and either they knew it, or they did not. If they knew the song, they fired right up and began playing and singing the song, and their audiences loved every note and word. Ironically, many of these folks were excellent readers and highly trained musicians, but you would never have known it when they were on stage.
All the best,
Gary
