this is something i know practically nothing about. anybody care to explain from the beginning? i guess starting with the blues or something... i dont know

it's not something that can really be explained in one sitting...

who said im only here for one sitting?

what sort of things are you looking for ? chord structures ? scales ?
I"m not a jazz player, but adding 7th, maj7, add9, etc. into the chords can make your playing sounded jazzy. IMO, learning jazz is more like learning the groove.

i want to learn the basic concepts behind jazz and the evolution of those ideas. not so much the different scales and chords you can play but why you play them

Check out this site:

Jazz Theory

For guitarists, the best book I've found to start with is 'Jazz Guitar' in the Hal Leonard series. It explains things really well.

A really important concept in jazz is chord substitution. The article in the link there looks really complex, but at heart it's quite a simple process, as long as you're good at chord spellings.

It revolves around the fact that many chords are similar or rearranged versions of each other. The simplest one is C major, which can be thought of as A min 7 with no root.

Simple substitutions involve extending the basic chords you're working with. So, instead of C major, you could play C major 7, C major 9, 11, 13, or any combination of these with raised or flattened notes depending on what sound you want. Since there are so many possibilities, it's best to start off simply and build up your vocabulary of chord progressions.

Another good sub is to take any seventh chord, and then substitute it with a half-diminished chord a major third higher. Example:

For A7, an obvious sub to go for would be A9. However, you could also use C# min 7 flat 5, which is an A9 with no root. The bass player will probably play the root, so you can get away without it.

The reason why you play these chords is to give your music variety and to take advantage of the huge possibilities that harmony has to offer. Playing in a jazz group and sticking to basic chord sequences with no variation would sound dull after a while, and very un-jazz-like.

As always with music, the key thing is to practise and keep training your ears.

From a pianist's perspective: I took jazz theory last semister and found it enjoyable. The point of jazz is to be heavily improvized. When you get a lead sheet of jazz music it will just have the "head" or main melody layed out as just single notes, like what you would sing. And it will also have the chords written above each measure to tell you what to play for harmony. Jazz chords have a little bit different symbolism than classical chords so it would be best to learn those first.

The second part of jazz is to learn all the possible substitutions for the chords you are trying to play. Since you have the head and the chords you can't just play those things over and over again, you need to learn to substitute, that's what keeps the music interesting. Most classic jazz tunes are pretty short, you have to improvise to keep it interesting through the 6-8 repeats you most likely will do. Start with learning chord inversions, jazz music heavily uses minor 7th's so practice inversions with the 7th's. When playing alone it is best to play as many notes in a chord as you can, if you are playing with a band you really want to cut down on how many notes are in each chord, this keeps it from sounding muddy and overpowering the rest of the band. I started by simply practicing octaves in the left hand along with the 3rd and 7 being played in the right hand. This leaves the chord very open for improv as well as limiting its power.

There are so many different types of substitutions for jazz chords it's unbelieveable. Very open ended. Hell, even if you hit a wrong note it sounds good sometimes. There is another substitution called tri-tones. A tri-tone is the flat 5th of any chord you are playing (called a tri-tone because it is exactly half way between the octave of the two roots of the original chord). So if you are playing a C, the tri-tone of C is Gflat. There is a trick to substitute tri-tones for the original chord since it contains alot of the same kinds of characteristics of the original chord and gives a nice contrast, If you play a diminished flat-5th then it will contain the root and 6th of the original chord and that sounds even nicer. Even if the rest of the band is playing the original chord you can throw in a tri-tone and it will sound pretty nice. I really didn't have a whole lot of time to explore tri-tones in class. We were just getting into them before the semister ended.

Jazz bands usually go in rounds, meaning each musician trades off on solos. This is probably the hardest part about jazz. You've got to know every scale like the back of your hand and be able to switch to different scales incredibly fast. In theory you could just play anything and it would be an improvised solo but the goal is to play something that sounds cool so here are a few tips for practicing solos:

-Hum or sing the notes you want to play. This forces you to think about the melody you want to make a split second before you try to play it.

-Work off the head. If you know the head really well then you can play that and add in notes and accidentals to make it sound different.

-As well as knowing the head, know the chords that are supposed to be played in that measure then you can also do some arrpegiations.

-If you are in a tight spot you can always just improvise some melody completely until you can get back to where you are supposed to be. A nice trick I learned for this is to stay between the 3rd and minor 7th of the chord being played. If you go below the 3rd it sounds to much like you are leading to the tonic and if you go above the minor 7th the same thing happens. It sounds like you are closing your solo, usefull if you really are trying to close.

If that is the case I suggest you just play a bunch of jazz pieces and listen to jazz music until you understand how it sounds and the rhythm, ect. That is probably how I would learn it myself, I am a hands on type of person.