I already showed you how to effectively add a altered Dominant a fifth above (or a Lydian Dominant a half-step above- same difference) the chord you are on (or going to) by playing a melodic minor scale a Major third below the target chord. I'm reposting an example of this below to refresh your memory:
(click on the above graphic for a larger version)
There are some other harmonic techniques that I often use along the same lines as the above example. One of the first rules of chord substitions is that you can add a related V7 before ANY chord. This means that I can use any type of dominant scale option, not just a mixolydian scale. Actually, the more alterations use use in these added dominants the better. This is because you want to create enough dissonance so that when you do resolve to your target chord there is a strong resolution. For example, if you were adding a passing V7 to a bar of CMaj7 and you chose G7 mixolydian then it wouldn't be clear to the listener that you were adding anything because you'd still be in the same mode.
/ CMaj7 /G7 /CMaj7 /
Of course this example works fine and is one of the most common types of chord substitution, but if you play a single note instrument there isn't much you can do with this most basic added V7. Instead we want to look for dominant scales with more alterations to use for our added V7s.
Below are the formulas for quickly finding scales for added V7s. These V7 can be used as passing chords over static chords, as added V7 before moving to a new chord in the progression, or as a way to create a delayed resolution. For these examples I'll use the passing V7 of a static target chord of D-7. So imagine we're playing Impressions and looking for ways to momentarily move outside by playing the related V7 of D-7, which is A7.
1. Pentatonic up a half-step from target: Eb pentatonic= A7alt= (#11, b13, b7, b9, #9)2. Whole tone up or down a half-step from target chord: Eb w.t. = A+73. Diminished down a half step from target chord: C# diminished= A7(b9)4. Major triad half-step above target and Major triad a minor third above target chord: Eb Maj + F Maj=A7alt5. Melodic minor a Major third below root of target chord: Bb melodic minor= A7alt6. Melodic minor a whole-step above target chord: E melodic minor= A7(#11)7. Harmonic Major up a minor third from target chord: F harmonic Major= A7(b9, #9, b13)8. Harmonic minor down a Major third down from target chord: Bb harmonic minor=A7(#11, b9, #9, b13)