In our first blues soloing post we looked at the minor pentatonic and blues scales. These scales work well over the whole basic 3 chord progression, but if we want to address the chords more specifically as they change we need to look at other options. The IV chord C7 is the first chord we are going to look at.
The C7 chord has the notes C E G Bb. The two most important notes in this chord, the ones that define it as a C7 chord are E and Bb (3rd and b7th).
Our G minor pentatonic scale already contains three of these notes G Bb C, so we only need to add the E to really target the strong tones in the C7 chord. The two scales below only differ by one note. The G minor pentatonic is G Bb C D F, and the C dominant pentatonic is C D E G Bb.
The C dominant pentatonic scale can also be considered a G minor pentatonic scale with a 6 (E) replacing the b7 (F). Because the scale also contains the 9th (D), it sounds particularly effective when playing over a C9 chord.
The formula for this scale is Root, 2nd, 3rd, 5th, and b7th. For C7 that would be C D E G Bb. Or you can think of it as a minor pentatonic scale starting on the 5th of the chord (G) with just that one note changed (the 6 replaces the b7).
Here’s the five positions of the scale for the C7 chord
This scale works well on unaltered dominant chords. An altered dominant could have any or all of these alterations b9 #9 b5 #5. Our scale has the unaltered 9th and 5th, so is a good and (safe) choice for unaltered C7 chords.
We could also use this scale option for the I and V chords G7 and D7, which now gives us the choice of using the G minor pentatonic and/or blues scale over the whole progression, or using a different scale for each chord to outline the changes. Here’s the scale for G7.