C# is D flat: Lick over dominant 7(9♭)

The last couple of days I have been trying to practice over the II - V - I cadence of chords, training both chord and scales. There is one particular scale that I really wish I could master. I find particularly challenging to apply such a scale. I'm talking about the altered scale.

It is a very rich scale in terms of sonority but when I play it note by note it sounds really odd to my ears - maybe that's why I personally find it difficult to use. This scale is mainly used over the dominant chord, and sounds very jazzy. I like to play metal solos but I'm stuffed to listen to pentatonic scales, for years I've been trying to add a little bit of fusion to my metal solos, I think it adds much more colour and tension to the sonority.

The altered scale is composed by the intervals: 1 - 2♭ - 2# - 3 - 5♭ - 5# - 7m. In some texts the 2# (which is the 9#) is written as 3♭. Although they refer to the same note, I prefer to emphasize its augmented ninth nature over a minor third. All the notes of the altered scale truly reflect some of the possible combinations a dominant chord can has:

V7(9♭) - V7(5#) - V5# ...

I've written two licks over the chords G7(9♭) and C7M. When I wrote the first one I was thinking in the very close relationship that the V7(9♭) chords have with diminished chords. If you play 7(9♭) chords every whole and a half tone you will notice that the sound you get is very similar to the one produced by a sequence of diminished chord - example:

G7(9♭) - E7(9♭) - C#7(9♭)
Fº - Dº - Bº

... and as diminish chords (include here 7(9♭) chords) are symmetric, you can substitute one by another.

So coming back to the topic, the first lick starts with the notes of the diminished scale (ascendlinging) and come back descending in the scale using the notes of the C#7M arpeggio (or the notes of Fm7 if you wish) - and yes the I#7M chord can prepare the I7M.