Pay the highest tip to musicians from whom you have requested a special song. Requesting a selection from a performer at almost any venue should involve a significant tip, and the fancier the venue, the higher the tip. Tip more at your country club than you would at a regular restaurant or cafe, even if you made a musical request at all three. You could tip anywhere from $5 to $20 or more.
Spend what you feel is warranted when you hear a favorite song being played in a restaurant but you did not make a request. Put the money in a tip jar if one is left out, or you can slip the money to the musician after the performance, or to your waiter or hostess to pass along so you won't disturb the performer. Pay anywhere from $1 to $5. If there is no tip jar and it feels uncomfortable leaving a tip, a kind word on how much you enjoyed the performance is always appreciated.
Avoid leaving a tip if you have not enjoyed the music. If strolling musicians at restaurants leave you cold, simply ignore them and they will wander off to serenade the patrons who do enjoy their music. Tip only when someone in your party has truly been entertained. Tip strolling performers you enjoy $1 per musician. Double that if you make a request.