In this part of our series on Blues soloing, we will look at the use of the melodic minor scale when improvising over Dom7 chords. This is a very useful sound in a Jazz type blues, but it just might sound a bit out of context in a John Lee Hooker tune. For our I chord G7, (G9, G13) we will use the melodic minor scale whose root is a 5th away. This will give us the ascending form of the D melodic minor scale D E F G A B C# (which we use when both ascending and descending the scale). The chord tones are root, 9th, b3rd, 4th, 5th, 6th, 7th.
For the C7, which is unaltered, the same formula gives us a G melodic minor G A Bb C D E F#.
For D7, we can use the same formula if the chord is unaltered. This would give us A melodic minor A B C D E F# G#.
If the D7 is altered we use the melodic minor scale a semitone above (Eb melodic minor). This gives us Eb F Gb Ab Bb C D. This gives us the chord tones root, b9, #9, 3rd, b5th (#11th), #5th, b7th.