The BLUES SCALE is indigenous to America, and is probably the most frequently played scale in popular music today. You can hear it anywhere from Blues (of course) to Rock to Country to Folk ...AND JAZZ.

The most popular version of the Blues scale is the minor blues scale. It contains all the notes of the minor pentatonic scale, plus a 'd5' interval (between P4 & P5, called the 'Blue Note.' The inclusion of this Blue Note is most likely derived from many Blues artists (namely vocalists, guitarists, harmonica players and other wind instrumentalists) who would frequently bend the 4th scale-tone up a half-step, as heard an many Blues recordings.

As with the minor pentatonic having it’s relative Major pentatonic, so does the minor blues scale. It's relative is based off the 'm3'rd interval (as shown below). As you can see, the blue note of the Major pentatonic is a 'm3' (between M2 & M3) interval, which is identical in pitch to the relative minor pentatonic blue note. An interesting thing about both, the Major and minor blues scale is that they are sometimes (but not always) played contrary to the chord changes. You may hear the minor blues scale improvised against Major or dominant chords with their Major 3rds, and then you may hear the Major blues improvised over minor changes (though the latter is much less frequent). This creates musical tension which adds spice to the sound, giving you that bluesy effect.

COMPOSITE BLUES SCALE: Here is an interesting approach. Combine both the Major and Minor Blues scales in parallel (from an identical starting pitch). This will give you a more complete set of notes which will enable you to form hybrid phrases of both the minor and Major blues scales.

You'll also notice that the composite blues scale contains all the notes at some other scale/modes such as the Mixolydian mode (omit the m3 & d5 Interval) and the Dorian mode (omit the M3 & d5 interval). You can then construct the 'Lydian Dominant' (Mixolydian w/ #4 Interval) a popular jazz mode based off the Melodic Minor scale. You'll also notice that the Composite Blues scale contains the notes at the diminish seventh arpeggio. Once you have discovered these other scale possibilities, go ahead and experiment some more by adding, omitting, or exchanging tones from within the composite scale and see what you can come up with.

The following examples illustrate how these ‘Composite' modes can be used for blues improvisation: