QUOTE(jinxi @ Apr 28 2008, 08:45 AM)

Just taken ABRSM Grade 1 jazz piano and am taking grade 2 this term. Am really enjoying the music and the opportunity to improvise, but I know I'm relying very much on my ear and I don't even have any basic knowledge of jazz theory. I've got A level music and Grade 5 theory, taken many moons ago (can hardly remember anything) but, to be fair, I was always pretty rubbish at the theory side of things. I've got a good ear (I think) so my teacher is really pleased with my impros. They come easily and sound authentic enough, but I know that if I want to progress to the higher grades, I'll need some knowledge of jazz theory. I'd also like to get to the point where I can vamp along with things using chords rather than relying on notation all the time. I can do it, but only at a very basic level.
I've looked at books, started reading things but I think I'm the kind of person that needs to learn things in context i.e. through doing. (To be honest, I start reading a page about jazz theory and my eyes start glazing over! I've always been the same about theory...)
Any suggestions? I was just looking at some of the City Lit courses, which look good. I see they suggest a basic 'pop' course before starting on their jazz piano courses. Trouble is, I've got a busy job and a small child and it's always a struggle fitting everything in.
Any thoughts welcome...
(You mentioned City Lit.) Many years ago, I went to jazz piano evening classes at Morley College, London (beginners' and advanced classes were offered). I thought they were very good, but a lot depends on the particular tutor, of course. I'd recommend seeing if they're still running.
When I was there, you could go to one class at the start of term before deciding whether to pay to continue. Being something of a jazz-playing novice, I first went to one session of the beginners' course but it was way too basic. With some trepidation I went to an advanced class. As I walked in, I thought I'd made a dreadful mistake and would be hopelessly out of my depth, because half the people there were older-looking males, who I assumed were all well-experienced jazz players. But it just turned out that OAPs got in free (or very cheaply).
Being part of a class was very helpful - more than is measured just by the relatively small set of facts that you acquire by being there.
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You're lucky you already seem to be good at jazz improvisation (which, sadly, I've never really become good at, despite being quite good at musical improvisation in other contexts). I think what you mainly need to add to that are: (a) getting jazz harmony to come naturally; and (b) listening to jazz to get a good jazz feel into your playing.
Do, of course, let the theory you learn IMPROVE the way you play, not DETERMINE it. You say you rely a lot on your good ear - IMHO you OUGHT to.
Depending on what kind of jazz you want to play, there's a lot of stuff that you could take seriously - or not - such as learning fairly standard LH voicings for chords - these assume there's a bass player and that you'll not only expressly avoid playing a bass part, but will also mainly play LH chords with the roots left out - they REALLY don't look like the chords you would have done in A-Level music. But, however quick your brain is, you probably can't work out suitable chords and voice leading afresh every time you play. Some people recommend rigorous learning of "II-V-I" LH voicings in all keys (because that chord progression appears so often in some kinds of jazz). You could skimp in that whole area if your interest is in a type of jazz where that's less important.
There are numerous books that cover all that.
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I, for one, am particularly fond of jazz harmony. If you ever just want to sit at the piano and play a familiar song tune (straight without improvisation), the use of jazz harmony gives you a lot of options and a lush palate - I think it's worth learning just for that aspect alone - though you mustn't get so that you always use those chords out of habit.
To start, at very least find out soon what jazz people mean by "tritone-substitute", and be sure to know the sound of "sharp ninth" chords. [Exercise: play this dominant thirteenth chord - B flat, A flat, D, G; then replace the B flat by an E.] Then try randomly stacking simple triads on top of dominant seventh chords, and on top of the major and minor diatonic chords of a major key, and you'll soon stumble into ways of creating a lot of the colour that you hear in jazz. Also look for ways of constructing familiar chords by, as far as possible, stacking fourths instead of thirds.