In jazz, we usually don’t say “rep”, but the idea or concept is obviously the same! Usually, the more tunes you know, the better off you’ll be in most jazz settings.
Most don’t realize this but in jazz, knowing a lot of tunes can inform your improvisation skills, especially if you play the tunes in their appropriate styles accurately. In other words, if you can play “Donna Lee” like the bebop tune it is, then it can help you play better in the bebop style.
There are so many ways/reasons why I choose what I am going to play at a gig/in a recording session/at a jam session, but here are a few:
1. I hear a peer playing a tune I don’t know
As jazz musicians, we are constantly learning. Sure, there are those cats who know a million tunes, but I can assure you, no one knows EVERY TUNE EVER WRITTEN. There are tunes like C Jam Blues and Autumn Leaves that every jazz musician should definitely know, but there are standards that I still haven’t learned.
2. It’s a difficult tune that no one really knows/I’ve been dying to get around to learning
Personally, it’s a cool feeling when you know a tune that you don’t think most people around are familiar with. It’s an even cooler feeling to put your fellow musicians on to a new tune.
3. I just love the tune!
There is no shame in playing tunes you love. More often than not, you’ll probably play the tune better since you love it so much! (That was my relationship with All the Things You Are for SO long!)