Dominant 7ths on the Blues
As I mentioned in the Blues lesson applying the Root-5th-Flat 7th-Octave pattern, the dominant 7th chord is a key component to the blues and the overall blues sound.
You should recognize that you’re only adding one note to the major triad the flat 7th.
A lot of blues basslines will emphasize and revolve around the chord tones for each dominant 7th chord. Even if other non-chord tones are involved, the chord tones are the backbone of the bassline.
In the exercises there are two basslines that strictly stick to chord tones. As a result, you can really hear the chords in the bassline alone. If you played the basslines without accompaniment there would still be no doubt as to what the current chord is and that you were playing the blues progression. Your job as a supportive bass player is to lay down the time (rhythm) and lay down the harmony.
Just as with the other blues basslines so far, you should practice them on your own at various tempos and in other keys.
I can never emphasize practicing your creativity enough. See what you can come up with on your own applying these same ideas. Experiment with different rhythms, repeated notes, changing the order of the notes, etc. Do it even if you think it stinks!