Wednesday, January 13, 2010

Thinking Outside the Box from Inside the Box


    The box I'm talking about here is the infamous "minor pentatonic box"  (shown above) which guitar players seem to love so much.  This box pattern is usually the first thing guitar players learn when first dealing with improvising over a blues progression, so most guitar players should be very familiar with this scale.  In this article I will be demonstrating how one could use this scale to play over a ii-V7-I progression, which is a common sequence used in jazz.

    I'll use a ii-V7-I in the key of G major as an example (Amin - D7 - Gmaj).  The most obvious scale choices used to play over these changes would be A dorian for the Amin chord, D mixolydian for the D7 chord, and G major for the Gmaj chord.  What if I told you that you could use a different minor pentatonic scale for each of the 3 chords in the progression?  You may think I'm crazy, and I may be, but check this out.

    For the first chord, Amin, we can use the minor pentatonic scale built from the note a fourth down or a fifth up.  Either way, you arrive at E, so the E minor pentatonic scale is the one I'm talking about here.  Let's compare A dorian with E minor pentatonic.  A dorian is comprised of the notes A, B, C, D, E, F#, and G.  Looking at E pentatonic minor, we see that it contains the notes E, G, A, B, and D.  As you can see, all the notes in the E pentatonic minor scale are also found in the A dorian scale.  No qualms there.

    Moving on to the D7 chord, we can use the minor pentatonic scale built from the note a minor third up or a major sixth down, F.  Comparing D mixolydian and F pentatonic minor, we see that D mixolydian is made up of the notes D, E, F#, G, A, B, and C, and F pentatonic minor is comprised of the notes F, Ab, Bb, C, and Eb.  At first glance these two scales are seemingly unrelated to each other.  To explain why this scale works over the D7 chord in this situation will require us to understand a little bit about the function of the 7th chord in this situation.

    In a ii-V7-I sequence, the V7 chord is providing the dominant function of the key.  This means that it's purpose is to create tension which will be resolved at the sounding of the I chord, which is the home chord of the key.  There are many ways to produce tension on a dominant chord, one of which is altering some of the tones of the chord itself.  A V7 chord is built as follows from the root:  Root, 3rd, 5th, flat 7th.  The tones we can add to or alter the V7 chord to produce tension are the flat 9th, sharp 9th, flat 5th, and flat 6th.

    Let's go back to the F pentatonic minor scale over the D7 chord.  We can see that upon closer examination, the F pentatonic minor contains the flat 9 (Eb), sharp 9 (F), flat 5 (Ab), and flat 6 (Bb), all of the possible altered tones you can have on D7, as well as the characteristic flat 7th degree of a V7 chord.  Now you can see why this choice of scale is not as outrageous as it first seemed.

    Now for the the I chord (Gmaj).  Instead of using the G major scale, which would be the obvious choice, try using the minor pentatonic scale built from the note a half-step down or major 7th up, F#.  The G major scale consists of the notes G, A, B, C, D, E, and F#, while the F# pentatonic minor scale is comprised of the notes F#, A, B, C#, and E.  The only seemingly disagreeable note here is the C#, the raised fourth degree of the G major scale.  Even though this note is not in the key signature of G major, common practice has dictated that the use of the raised fourth degree over a major chord is quite acceptable.  It has become such a common sound that most jazz instrument teachers will teach you to use the lydian scale over a major chord instead of the major scale.  The lydian scale is simply the a major scale with a raised 4th degree, so G lydian would be G, A, B, C#, D, E, F#.

    If you didn't notice, each of the minor pentatonic scales which I described above are a half-step apart.  That's right, instead of calculating the interval from each chord to build the minor pentatonic scale from, just calculate the interval from the ii chord, and then move up in half-steps.  So for a ii-V7-I in C major (Dmin - G7 - Cmaj), just think a fourth down or a fifth up from Dmin, which is A.  Then just move up a half-step for each consecutive chord: A pentatonic minor, then A# (or Bb) pentatonic minor, and finally B pentatonic minor.

    This is a simple, yet highly effective means for improvising over one of the most common chord progressions found in jazz: the ii-V7-I.  Please let me know what you think in the comments.  Any and all feedback is much appreciated.




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