Looking for some increasingly edgy scales to play over that D7 chord?
It can be helpful to think in this case in terms of the C lydian mode as the basic scale (instead of the conventional major scale) and then look at its increasingly altered cousins as improvisory substitutes. All of these contain a #11 from the tonic (i.e. a F# based on a tonic C for the scale). These show themselves as a 3rd and b7th in a D7 chord.
Why the lydian mode I hear you ask?
Because it is the only 7 note mode (derivable from any starting or parent 7 note scale) containing notes which can be completely restructured in 5ths. Descending 5ths are the order one generally follows in completing a cadence. A II V I sequence (for example A D G in the key of G) is a simple example of descending 5ths. The significance of this is that the lydian scale can be restructured into a chord using all the notes of the scale and this chord feels very much at rest as the final chord of a cadence in a major key.
Let’s expand. The lydian scale in C is: C D E F# G A B. The descending order of 5ths is F# B E A D G C. The corresponding chord C Maj (#11) using stacked thirds is (from the lowest note to the highest) C E G B D F# A (ie 1 3 5 7 9 #11 13). Play it. It sounds so much more at rest than the corresponding chord constructed from the C major scale (C E G B D F A). The F is an avoid note but F# isn’t (in this context).
Those familiar with modes will know that D7 is usually thought of as being derived from D mixolydian, the 5th mode of G major (G ionian). C lydian is the 4th mode of G major. Thus, it is clear and obvious that C lydian can be played over D7. Any mode derived from G major can be played over D7. So why pick C lydian? The reason is that the notes of C lydian form the innermost notes of a much larger (chromatic) scale which descends in 5ths (as though under the influence of gravitational pull). This scale may be called the pure lydian chromatic scale. In ascending order of 5ths it is C G D A E B F# Db Ab Eb Bb F. The first 7 notes are the notes of C lydian, reordered in 5ths. This is the innermost 7 note scale of all the 7 note possibilities that could arise from the lydian chromatic scale. Note that F is the outermost note – the one that sounds least at rest in a C universe.
So, C lydian scale sounds fine and natural over the D7 chord. A slightly more edgy scale to play over D7 is C lydian #5 (also known as C lydian augmented). Here we have substituted G, the second-most “in” note in the lydian chromatic scale, with one of the “outer” notes Ab. The C lydian #5 scale is C D E F# G#(Ab) A B. Try it over D7 (I suggest you use D F# C as the voicing of the chord in the first instance). Those who know their modes will know that the lydian #5 is the 3rd mode of A melodic minor. The combined sound is that of D7(#11).
If you are interested in seeing more on this subject, tune in to Jammers eNews for PARTS 2-5. The material presented in this series has been derived in the main from principles set out in George Russell’s intriguing book “Lydian Chromatic Concept of Tonal Organisation Vol One: The Art and Science of Tonal Gravity”. This book was published originally in 1953. The 2001 edition is published by Concept Publishing Company. This is a book well worth getting your mind around if you are interested in this area. To the best of my knowledge there is no Vol Two. Some of the material presented is at variance with Russell’s, mainly to do with the fact that he puts Db (ie b9) at the end of his Lydian chromatic scale (after F) he says to better accommodate Western harmonic practice but I don’t think this is necessary and it also spoils the pureness of the Lydian chromatic scale in 5ths. Also, Russell does not utilise any Lydian-based modes derived from the harmonic minor scale. This appears to me to be an unnecessary omission.
END OF PART 1