Since my first Jazz experience, which was a bit harsh, I’ve learned quite a few things about it that de-mystifies this field of music that is feared by so many.
It basically comes down to standards: All of Me, On the Sunny Side of the Street, Cantaloupe Island, Out of Nowhere, Donna Lee, Anthropology, Mr PC, Take The A Train, Sunny… being the most common.
At least in my experience, playing all the songs always ends up as a good session. It might seem like quite a lot of songs but at a basic level it’s just some chords in a loop. And also at a basic level you can pretty much solo with one scale all the way through. So now you can play jazz too, as I’ve redundantly said, a basic level without needing to study anything that you didn’t already know.
But it is at this point when Jazz gets a bit complicated, and also very interesting. To sound jazzier it comes down to 2 fields: comping and scales. As far as I know Jazz is always taught applying a scale to a chord from the standard, which I always thought was stupid because you end up playing the same notes but in a different order. Where it gets interesting is when you alter the scale to fit the alterations of the chord, or even fit a weird scale, just because it shares three notes with the chord. And now is when your jazz solos start to sound weird but satisfying jazz cacophonies.
Using chromatisms in the right place spices up your sound too. And now to the bit where you’re not soloing, but comping. What I have concluded is: use as many chord alterations as you can (6, #9, 13…) by doing this you’ll end up with very weird shapes but it’ll sound like a weird but satisfying jazz cacophony. Another trick is to use secondary dominant substitutions which is to substitute a seventh chord for a seventh a sharp fourth higher. This plus a tone of alterations gives you the almighty Jazz sound.
Well, here’s how I learnt jazz all by myself, progressively, reading what I just wrote.