Here is how to say no in these 3 common situations.
- No to a gig: When you don't want to take a gig, emphasize how much you wish you could have done it, how sorry you are that you can't, and how you really wish you could have done it. And then make sure to recommend the absolute best players you know for it.
- No to a rehearsal or a lesson: To say no to playing for a rehearsal or a lesson, simply say that you are unavailable, without explaining why.
When people insist, say that you'll double check your schedule, but do not take your calendar out in front of them. Otherwise you run the risk of people taking a peek at it, and of you saying yes before you even had the time to understand what happened.
- No to sight reading a piece in public: When someone asks you to sight-read the equivalent of, say, a Rachmaninoff piano concerto in public, ask the soloist what other pieces he or she is working on to hopefully find one that would work for both of you.
If he or she insists on that one particular piece, say that you'd rather play it at the next class, after you'll have had a few days with it.
Picture from http://www.dailymail.co.uk/news/article-1023318/Thousands-protesters-create-gigantic-NO-sign-march-Heathrow-expansion.html