In my study of jazz improvisation pedagogy, I've noticed a relative scarcity of instruction related to the whole-tone scale and the augmented chord that derives from it. There is quite a bit of information on the lydian-augmented scale, which is the 3rd mode of the ascending melodic minor scale, but even here there is a lack instruction on how to apply the scale in context. It seems to me that most of the literature focusing on scales does not go far enough in explaining the application of such scales in the context of the entire structure of real songs. In other words, it's easy enough to see that particular notes of a scale (i.e. the intervalic distances from the tonic) correspond with a particular chord (especially its altered extensions) but what are the possible functions of a scale or chord related to the surrounding changes in a song?
The augmented scale has intrigued me since I first learned about it in junior high school. I was taking saxophone lessons from a guy that got me interested in jazz improvisation. I had learned to write and play all of the major and minor scales (both melodic and harmonic) from memory and I wondered what other scales existed that I might have to memorize, hoping there were none. That's when my instructor embarked on several lessons in scale and chord construction and the limitless possibilities of sound using only the 12 tones of our Western chromatic scale. The first thing he showed me was that scales could have fewer or more tones than 7 (the number of tones in the majors and minors) and proceded to write out the formula for constructing a whole-tone scale : 1-1-1-1-1-1 (he always wrote scale formulas in terms of the intervals between successive notes, so a major scale would be written 1-1-1/2- 1-1-1-1/2). When he asked me to play a whole-tone scale starting on C, I was blown away by how accustomed I had become to diatonicity. My fingers had a hard time finding F# and G#. The B-flat (as I thought of it, instead of A#) was not as foriegn because I was used to playing the mixolydian modes, with their flatted sevenths. What really intrigued me about the whole-tone scale was that there are really only two of them (and only 4 augmented chords).
I've been trying to figure out how to use the whole-tone scale and the augmented chord in my improvisation ever since my first revelation. One of the first things I discovered is that the augmented 5th naturally resolves upward to become the major 3rd of the next chord. So a C+ chord naturally moves to F major. In other words, an augmented chord functions like V7 leanding to I. This is useful for the end of a song that ends on the V because V+ will naturally lead to Imaj, and this is can be heard almost as a signature in many older R&B and do-wap songs. It's fun to put a V+7 at the end of a blues progression. The disonance of the whole-tone scale can be suspended for a greater length of time in this situation because the tension is usually the greatest here and the listener expects a resolution on the downbeat of the next chorus. A III-VI-II-V-I turnaround offers an opportunity for whole-tone utilization because the III, VI, and II are really just substitutes for the V and the whole sequence functions as single dominant leading to the tonic. Playing a line on the whole-tone scale I+ just before the change to IV can add a sense of playing "outside" or ""sideslipping" but this opportunity comes and goes quickly as the tension and resolution of a I-IV near the beginning of the chorus does not have the urgency of a V-I progression. I've been trying to think of a way to keep the dissonant energy of a whole-tone line going from the final V of a blues chorus, through the I at the start of a new chorus, all the way to the IV in the 5th bar but I've not been successful in pulling this off (yet).
I've had quite a bit of success playing whole-tone patterns in modal playing, especially "one-chord" tunes where playing outside is almost a requirement to break the monotony. In a recent extended solo on Chain of Fools (known euphemistically by our band as Chain of Chord, or sometimes just Chord), which is in C minor, I managed to build the tension up through the use of chromaticism and a neopolitan minor scale to 8 bars of whole tone figures on E-flat. This had the effect of adding a flatted 9th to an ascending C melodic minor while omitting the root. A few obtuse counter-figures from the rhythm section really polished off the effect.