Raise one note a half-step - observe what chord is formed.
Here is a 10-page PDF file that outlines Pat Martino's approach: This is far too complicated to cover in a few paragraphs, but the main thing is it is another way of viewing harmony, which gave me some fresh ideas. I'd be sure to have a thorough understanding of it before I went into the Concept, because traditional theory is how you are going to be communicating with other musicians. That being said, traditional theory will go a long way toward understanding most of what you hear and play. The long and short of it is that there are several options in any situation, and the Concept is a tool to help you decide which you prefer. This is grossly over simplified, and maybe doesn't make a lot of sense as I explained it.
Once it has been decided which is best for the vertical moment, we now know which scale to play horizontaly over the chord change. Our decision would be which tensions to use. Say, for example, we were going to consider each chord change in a vertical sense, and at this moment the chord is C Maj7. Something that is often overlooked in discussing the Concept is that it is based on the "vertical now" which occurs during the course of a piece of music. (Not on aying steel is something I do for fun. In answer to Bryan's questions, first of all I'm primarily a jazz player. (Check with your public library about their inter-library loan program - in Maryland, I've been able to check out almost every music book I've ever heard of, without buying.) You'd probably get to a fairly equivalent level of knowledge if you memorized the heads and all the solos from a few hundred jazz songs, and then analyzed them for the reasons behind note choices - paperwork required, in either event. It certainly couldn't hurt to dedicate a few years to Russell, if the teaching style hooks you. On the other hand, Martino's other approach - organizing via diminished & augmented concepts - is something I'm really enjoying. I looked into the Russell stuff, and thought it to be a thorough review of harmony but with a slightly different starting point or "slant" - sort of like Pat Martino's "everything's minor" approach. In my opinion, if you can define the goals with specificity, choosing what to study almost explains itself. Is it playing freely in the chromatic sense, being able to call up any note combinations? Is it in making new & fresh chordal choices.
There are many different ways to get to the same place, so an assessment of what specifically you're trying to achieve is a good start towards deciding what to study.