The blues, as a genre, relies almost 99 percent on the minor pentatonic scale for soloing—even if the rhythm guitar or keyboard player is playing major chords! Blues almost always uses the minor pentatonic scale. Why? First of all, the only rule worth remembering in music is this: If it sounds good to you then it works. When you apply the minor pentatonic scale to a major chord progression, you get a clash on some of the notes, and not every note will sound sweet and perfect. This clash is what gives the blues its unique style. The earliest recordings show that blues solos always used the minor pentatonic scale for improvised solos and vocal melodies. A major pentatonic scale in a blues solo would sound out of place, even though theoretically you would expect a major chord progression to have a major scale.