A Scale For Every Chord

So far we have a pretty simple method of jamming: figure out the key of the chord progression, pick the similarly-named pentatonic scale and play notes from it. Throw in the blue note if it works.  For blues, use the blues scale based on the minor pentatonic even if it’s in a major key.

You could and should spend a long time learning how to do this well.   I personally was stuck at this level for years (not that I do it that well).  But I’m not going to make you wait years -- I’m going to move right on to how to switch between different pentatonic scales over the course of a progression.

We’ve reached the second way of improvising a lead: choosing a scale to play over each chord.  This is often a good way to go.  You don’t have to know the key.  The chords don’t all have to be diatonic, in the same major key.  Even though in your mind it’s simple because you’re sticking to the familiar pentatonic scales, it will sound more complex as you’ll end up using more pitches than just five from a single pentatonic scale, adding interest.

The idea is given a chord, you should be able to know which pentatonic scale or scales might sound good played over that chord.  I made up a system that uses the circle of fifths to solve this. I’ll explain it by example.  Let’s just list some chords and talk about what pentatonic scale you might use to jam over that chord.

Let’s start with Am7.  The notes of the chord are indicated with yellow and green circles.  The yellow circles are the root and the fifth.  I’ll call these the weak tones as you might typically leave these out of the right hand if you were playing the chord, because you can be pretty sure the bass or your left hand will cover them.  The green circles are the strong tones, the tones that give the chord its character.  I try not to leave those out.

A chord symbol not only tells you what notes to play, it tells you what notes not to play.  That’s what I try to get at with the red circles with slashes.  This is A minor, so don’t play a C#, which would make it A major.  Even though the root and fifth are weak and you might leave them out, you don’t want to insult them by playing their respective tritones, so the tritones get slashed too.

Note that in the circle of fifths, a tritone is a pair of notes diametrically across from each other (e.g. C at twelve o’clock and F# at six o’clock).  (Tangent: the same relationship holds in the circle of semitones.)  This makes them six steps apart on the circle of fifths, as far away as possible -- the most dissonant in some sense.  Since the pentatonic is five notes in a row on the circle, each pair of notes in the pentatonic scale is at most four circle-steps apart, so the scale can’t possibly include a tritone.  By the same reasoning, it can’t include a major seventh or minor second (semitone) either, as those are five steps apart on the circle.

The blue arc represents the pentatonic scale.  It covers five consecutive notes of the circle. The first (most counterclockwise) tick points at the name of the major pentatonic (C above) and the second tick points at the name of the minor pentatonic (A above).  The puzzle is to draw the blue line that covers the circled tones but none of the slashed tones.  If you can’t cover all the tones, try to cover all the strong tones.

So, in this image we conclude we can play A minor pentatonic over Am7, which is pretty obvious I suppose, but it’s nice to see how the system works.

Next let’s look at A minor.  It’s pretty much the same picture as for Am7, and arrives at the same conclusion: play A minor pentatonic (aka C major pentatonic).

I indicated an alternate scale in pink - D minor (aka F major) pentatonic.  It blows off the weak e in favor of an f, which seems odd in an Am, but when you play it it sounds OK.  It’s especially appropriate when the Am is the iv chord (i.e you’re in the key of Dm), but that kind of thinking brings us back to choosing a pentatonic scale based on the key, so I won’t belabor it here.

C major is kind of like Am7 without the A, except now the weak tones are C and G (so we exclude their tritones) and the strong third is E (so we exclude the minor third Eb).  We get the obvious conclusion of C major pentatonic.  If we exclude the weak C, we could play G major pentatonic, but let’s save that possibility for the next chord.  Approximately this same picture works for C6 (add the A), and Cadd2 (add the D), both of which imply C pentatonic.

Cmaj7 adds the strong major seventh tone (b) to the C chord.  In addition to excluding the minor third (Eb) the chord name implies we should exclude the minor seventh (Bb), as indicated.

In order to cover the strong tones with a pentatonic we need to exclude the weak root (C).  So the solution is to play G major pentatonic, aka E minor pentatonic.  The way I remember this is that a Cmaj7 is Em/C -- an E minor chord with a C in the bass.  Em means play E minor pentatonic.

Cmaj9 (which I didn’t illustrate) adds the D, and gives the same answer: E minor pentatonic.  Remember it by recalling Cmaj9 is Em7/C.  And of course Em7 means E minor pentatonic.

Let’s look at Csus4 next.  Interestingly, Csus4 and Fsus2 are the same notes: c f g.  But what’s different about these two chords are the notes you shouldn’t play.  In general a suspended chord implies no third, so let’s exclude the major third (E) and the minor third (Eb).

So, the suggestion is over Csus4 play F pentatonic.  This adds the D (the second) and the A (the sixth).   An alternative suggestion is to play Bb pentatonic, adding the Bb (dominant seventh) and D (second) to the Csus4.  This would be especially appropriate if the chord were C7sus4.

Csus2 has the same notes as Gsus4, but the same pentatonics to play as Csus4, namely F and Bb.  This is in contrast to Gsus4, where (by transposition of the Csus4 result) we know to play C and F pentatonics.  Same notes, (some) different scales.  Excluding the thirds of G (Bb and B) rules out the Bb pentatonic for Gsus4.











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