Doesn't this imply that you need a good memory to be "good enough" to play jazz. I think the hip thing or jazz attitude is not too related to be good...
Why would they laugh? It seems to be a convention to do this, as well as being very useful, it could save turning back to page 1 to find out what key...
I like them on every line, especially as I get older and my memory was not what it is. I don't quite understand your subject line though. Whether on...
If this occurs in a major cadence, e.g. C7 b13 to F maj7, you could actually refer to it as modal interchange, in the same way you might with Gbmaj7...
I don't think so, I've never seen that. If it is then it's completely superfluous because the notation shows that anyway (dotted minim is held up to...