After leaving the Jam at Ralphies Saturday I performed a duo gig with Lisa Bell that required me to read charts for 2+ hours. Many of the songs we never performed before so it was a learning experience!
If I had not grown up with an interest in all music this gig would have been impossible to do. If you want to do this for a living I would suggest listening to music from years ago. Show tunes, real book tunes, TV themes, songs that where made popular in movies and that are in the public psyche.
In the beginning focusing on what we love is great but value all music and learn what makes the different styles tick. You may never need to do this type of gig but it adds value to you as a person, musician, performer and songwriter.
Most happy with a guitar around my neck though it is starting to weigh me down!