I have tried (and failed!) to learn to play jazz more times than I can count.
It’s a dense and intimidating art form, and most of the instructional materials available read like a novel with the first 80 pages torn out.
So while I am far from well-versed in the ways of jazz music, in the past year I’ve made some solid inroads.
I’m amazed that what follows wasn’t driven into my thick skull from all angles when I first started trying to make sense of jazz.
1. Jazz is all about the timing.
If your time isn’t 100% on, you’re not going to sound jazzy. Developing a swinging groove & playing behind the beat is HARD. Learn to play with a metronome click on 2 & 4.
2. Jazz is about playing the changes.
You hear this phrase thrown around a lot, but pause for a moment to think about what it really means: you have to be hyper-aware of the chord being played (and the ones about to be played) and make appropriate note choices.
3. This means the biggest part of learning jazz is increasing your speed of musical thought.
You can train yourself to do this. iRealb is a fantastic app that’ll let you loop some tiny section of a song nice & slow.
4. Build up, don’t whittle down.
The root, the 5th, & the 9th all sound great too, but jazzers rarely resolve a line to the root–that’s more of a rock & blues thing to do. It’s possible that your ear is used to this sound and you’re playing it often, hampering your overall jazziness.
5. If you can make a chord tone of one chord move a half step to a chord tone of the next chord, you will sound jazzy.
For example, when you play F over G7 (that’s the 7 of G7), then play E as the chords change to C (now you’re playing the 3 of C), that’s playing the changes, and it sounds jazzy.
Get good enough at that and your solo will imply the chords so strongly that you’ll lead the listener’s ear along the changes, even if you’re playing unaccompanied.
6. Jazz is a modular music–you’re remixing the same chunks all the damned time.
The most common modular chunk of jazz harmony is the ii-V-I, but as you learn a few tunes, you’re going to see some others too.
7. Spend LOTS of time stealing from others.
Transcribe lines from players you like (and make sure you understand how the notes relate to the chords). Learn licks from the Charlie Parker Omnibook and the Aebersold ii-V-I book. Make them your own.
There’s so much more to be learned from this than you might guess…
8. Create a licktionary of all the lines you steal and/or create.
Write it in standard notation and it’ll improve your reading too. Practice finding them all over the neck, in all the keys…
9. Learn it in all 12 keys.
Once you have a line you like, learn it in all 12 keys. Being able to throw it down in all keys is massively helpful. And it goes a long way towards increasing your speed of musical thought.
10. Studying jazz will teach you almost everything you need to know to play in most styles.
Even if you don’t get to be very good at jazz, it still teaches you how to play successfully in just about every style––essentially everything but metal and classical.
But ain’t nobody going to pay you to play those styles anyway.
[note: I expanded this post from an answer I wrote over on Quora.]