Originally Posted by KingAenarion
This + one other thing.
One of the most helpful things I learnt when starting to play Jazz was this.
Chords and scales are the same thing. Think about them as the same thing, construct your chords with all the notes of the scale. Adding in more than just the basic triads give you different colours. Leave out the notes you don't want for particular colours...
And you can superimpose different structures for even more possible colors. You can super impose any interval structure over any harmony, the key is in emphasizing that structure.
So I might super impose an Em7 over a Cmaj7 by playing an E minor seven arpeggio root, third, fifth, seventh (E G B D). Might also superimpose by chromatically anticipating each of those with a piece of an E minor scale, or perhaps chromatically.
Another great tool is accents. I could play random notes, but if I accent chord tones on downbeats, it'll have an interior logic to it that makes it listenable (if played convincingly and with authority).
i.e. Over a Cmaj7, I might played any combination of the chromatic scale randomly all over the fretboard. As long as beats 1 and 3 (and less importantly, beats 2 and 4) feature one of the notes of an Em7, it'll imply an Em7 over Cmaj7 sound, producing an overall Cmaj9 harmony.
If there was an interior logic to this superimposition, it would sound even stronger. Perhaps outlining an ascending scale every second beat, with garbled nonsense chromatic notes inbetween. The ear will pick out the difference between the logical and illogical notes, and will follow the nonsense - especially if brought out with those accents.