I'm going to post a little demo of me going between str. 8ths, to shuffle, and then to a dotted 8th/16th. First sort of "morphing" between them and then going from one to another suddenly.
Why is this valuable. Well, there are many applications.
1. Modern ballad playing
When one is playing a slow tune in a Jazz setting, it's important to be able to hint at different feels at different times. There's nothing worse than playing a ballad and being stuck in a "12/8 prison" if the music doesn't require it.
2. Lots of feels call for "rolled 8ths"
Many times we'll play feels that exist somewhere between straight and shuffled. This happens in Rock, New orleans style, Brazilian, as well as many types of Jazz.
here's a fun example: Check out Ringo's hi-hat!
..Well I bet, you, I'm gonna be a big star!