Quickwrite -- Duty & Friendship

You have a date with your old friend you've known for 12 years next Monday. However, you just knew that there is going to be a band performance next Monday, too, and you must be in the band performance because you are one of the members in the band. Your friend who didn't see him for lots of years is going to be here next Monday, and you and he had already set the date, but as a band member, you can't be absent in the performance. What will you do if you are right in this kind of dilemma??
This is very hard to decide, because both are very important, you won't want to betray your old friend after all. There is going to be lots of chance to perform on stage in the band in the future, and the chance to meet your old friend is quite rare. If you are a trust friend, and you have a trust band member, I guess band members would like you to go see your old friend, and you'll be happy at that time, too.