A lesson in the recent Guitar Player magazine prompted to me to do a more
in-depth explanation of this cool concept, that straddles the line between
lead and rhythm playing: 6th intervals.

As you may know, chords are built in a succession of 3rd intervals.
Ex.: C,
E, G, Bb, D would spell a C9 chord. From each note to the next, there
is an
interval of a 3rd. C-->E is called a 3rd because there are 3 Major Scale
notes involved, C-->D-->E. When we use this interval, there are two
"colors"
of the 3rd: Major 3rd, and Minor 3rd. The chromatic distance between C and
E, that is to say all the notes, including the sharps and flats,
equals two
whole steps, otherwise found to be up 4 frets from C. This is the interval
of a Major 3rd. When we have a note a Major 3rd from the root of the
chord,
we have some sort of Major chord. The interval between E and G is a minor
3rd. Check on your fretboard to find that there is one less fret between E
and G, as contrasted to the C-to-E interval. This E-to-G interval is a
minor
3rd. Notice that in our dominant chord (C9), we also have another
minor 3rd
interval between the 5th of the chord (G) and the minor 7th note (Bb).
When
we call it the "minor 7th", we are considering the distance from the root,
C-->Bb. Again, the interval from the 5th to the minor 7th(sometimes
known as
the b7th) is a minor 3rd. The interval between the b7th and the 9th (Bb to
D) is a Major 3rd.

So, from the root to the next note, and then to each successive note, we
have a formula of: Major 3rd, minor 3rd, minor 3rd, Major 3rd.

If we invert these intervals we have minor 6th, Major 6th, Major 6th,
minor
6th. HUH? WHAT THE HELL DOES THAT MEAN? First of all, inverting an
interval
means turning it upside down, or putting the lower of the two notes on the
top. The C-->E Major 3rd becomes a minor 6th when you count from E to
C. Why
is that? Well, because a Major 6th is the 6th interval found in a major
scale between the root and the 6th note in the scale. C to A is a
Major 6th,
which is an interval composed of 9 half steps, or 9 frets. A minor 6th
would
be similar to the Major/minor 3rd phenomenon: the interval a half step
smaller than a Major 6th is known as a minor 6th.

What if we took the 3rds that are stacked in a dominant chord and inverted
all of them? Here's where we find the very cool lead/rhythm concept. Let's
start with inverting the C-to-E Major 3rd. This would turn out to be
E-to-C,
and might be played on the guitar like this:

e------
B---1---
G-----
D---2--
A-----
E-----

Play this with fingers 3 & 2 on the D string and B string, respectively.
There's a reason for this fingering, shown in a minute.

With this interval, you're not playing a chord, but you certainly have the
chord sound, no? Especially over a C bass, if you have a bass player
handy.
This is a minor 6th, but it gives us the sound of the C Major chord.

How about the next 3rd in the chord? E to G. Minor 3rd, but if we
invert it
to become G to E, we have a Major 6th. Finger it using the 3rd and 4th
fingers on the D string and B string, respectively. It should look like
this:

e------
B---5---
G-----
D---5--
A-----
E-----

Once again, we have the sound of the C Major chord, even though there
is no
C present. This especially works over a C bass.

We said that the next 3rd in this dominant chord was a minor 3rd too,
right?
So we would go to the next Major 6th. The third would have been G to
Bb, so
inverted, it should be Bb to G. It would be fingered the same as the
previous interval but at the 8th fret:

e------
B---8---
G-----
D---8--
A-----
E-----

This doesn't have as much of the sound of the C Major chord, but it
certainly has the dominant sound of the chord drilled into our head.
There's
no E in this voicing, but it works if there is another instrument playing
the chord, or if the Major quality of the chord has been previously
defined.
If you play the 5th fret then 8th fret Major 6ths, you have the C7 sound.

Okay, next 3rd: Bb to D. Inverted to become D to Bb, which is a minor 6th.
Finger like the first example here, with fingers 3 and 2 on the D and B
strings, respectively, like this:

e------
B---11---
G-----
D---12--
A-----
E-----

If you put these all together, you'd have a big ol' C9 chord. If you
were to
slide between them, changing to the appropriate fingering at the
appropriate
times, you would certainly be alluding to the C9 chord. You can play these
intervals as two notes together or one after the other. Clapton's take on
"Knockin' On Heaven's Door" features my second example, but in the key
of G,
like this:

e---7--5--3--
B-----------
G---7--5--4--
D-----------
A-----------
E-----------

This would be the D and B of the G Major chord to start with, the C
and A of
the diatonic dominant 7th chord for this key, D7, and then the last
voicing
is the B and G of the G Major chord. Notice also that the interval between
the 3rd string and the 1st string is a 6th, the same as the interval
between
the 4th and 2nd strings. These are the only two pairs of strings that you
can do this with, using these simple fingerings.

The fingerings I gave make it a simple process to change from Major to
minor
6th. You would keep your 3rd finger on the lower note of the interval, and
use either the 2nd finger or 4th finger to define the Major or minor
6th on
the higher-pitched string.

You can slide these intervals up and down the fingerboard, changing to the
appropriate Major or minor 6th intervals, and harmonize the entire Major
scale. Let's harmonize the G Major scale:

e--3---5---7---8---10---12---14---15-----
B----------------------------------------
G--4---5---7---9---11---12---14---16-----
D----------------------------------------
A----------------------------------------
E----------------------------------------

The first interval alludes to the G Major chord. The second interval
alludes
to the D7 chord. The 3rd interval alludes to the G Major chord. The 4th
interval alludes to the C Major chord. The 5th interval alludes to the D
Major chord(or D7 chord), the 6th interval alludes to the C Major
chord, the
7th interval alludes to the D Major or D7 chord, and the 8th interval
brings
us back to G Major.

But wait! Aren't the G and B from the first voicing also in an E minor
chord? Aren't the A and C from the 2nd voicing also in an A minor chord?
Aren't the B and D of the 3rd voicing also in B minor? Aren't the C
and E of
the 4th voicing also in A minor? Aren't the D and F# of the 5th
voicing also
in B minor? Aren't the E and G of the 6th voicing also in E minor? My,
that's a lot of questions, grasshopper. Go finish the dishes...

Yes, all of these are true. That's where the beauty of these voicings lie.
Additionally, you may find that the G and B from the first voicing work as
minor 7 and 9th of Am9, the A and C of the 2nd voicing also work as
6th and
root of a CMaj6 chord, B and D work as the 5th and 7th of Em7, C and E
also
work as b7 and 9 of D9, etc.

Do you need to know all of these intervals by name? No, not really. It
would
certainly be best to have an idea of the basic 3rds and roots of the
triads
that you're trying to outline and how to find the right 6th voicing, but
otherwise, it's best to work out the fingerings for the diatonic triads in
the key that you're outlining, and use your ears to find sounds that you
like best. You might like the E and G over the G chord, giving you a
Maj6th
chord, etc.

Check out tunes like "Soul Man", Clapton's "Help Me Up", tons of tunes
featuring Steve Cropper, Cornell Dupree, Eric Gale, Phil Upchurch, Robbie
Robertson, and many R&B, Soul, Blues, and Funk tunes. Of course, this
concept is certainly good for use in many different styles and
applications.