Help with sliding 6ths

[Bob Longo]

In particular, I'm trying to play Dobie Gray's "Drift Away" by ear. The guitarist is, I believe, sliding 6ths over the chords E and B and then over C#m-D-E into the chorus of B, F#, and E. My questions are:
What is the theory behind 6ths over chords? Or groups of chords?
Is there a progression for 6ths?
How can I apply this to other songs? Pete Townsend uses them a lot, and I'd like to apply them more in my playing.
Thanks.

[JonR]

6ths are the most consonant extension you can add to a major triad. They're very common as decorations in the kind of guitar playing you mention: soul/R&B ballads of a certain vintage - esp sliding up (or hammering on) from the 5th. Jimi Hendrix used them a lot when he played in that style (Wind Cries Mary, Little Wing, etc).
The other "companion" extension - again on a major triad - is the 9th. 6th and 9th complete the major pentatonic of the root (1-2-3-5-6). Soul/gospel vocalists typically sing (or improvise) on the major pent, hence the association of the sound. (Listen to classic Sam Cooke or Percy Sledge.)
Combine sliding 6ths with sliding 9ths - and double stops - and you get that classic vintage soul/Hendrix sound.
The great advantage of using 6 and 9 on a major triad is they will be in key on all three primary chords: I, IV, V. So you can freely improvise with the major pent of each chord, and everything will fit (plus you get that very sweet sound).

[Neer]

A 6th is just the interval between the lowest note and the highest note of the 1st or 2nd inversion triads. If you take a root triad (C E G), the interval between the bottom and top note is a perfect 5th. If you look at the first inversion (E G C), the distance between E and C is a minor 6th. In second inversion (G C E), between G and E is a major 6th.

So, the 6ths are just voices inside the chords that are moved up and down diatonically and chromatically.

[stevel]

Originally Posted by Bob Longo

In particular, I'm trying to play Dobie Gray's "Drift Away" by ear. The guitarist is, I believe, sliding 6ths over the chords E and B and then over C#m-D-E into the chorus of B, F#, and E. My questions are:
What is the theory behind 6ths over chords? Or groups of chords?
Is there a progression for 6ths?
How can I apply this to other songs? Pete Townsend uses them a lot, and I'd like to apply them more in my playing.
Thanks.

To add to what's already been said, usually what are called "parallel 6ths" are used very often to harmonize a melody line.

For example, if you have a melody that goes C-D-E, you could harmonize that with 6ths above, or 6ths below, depending on the harmony (or, what chord member of the harmony the melody note is).

For example, in C major, you might find:

C-D-E
E-F-G

In one sense, you're playing a C Major scale in one part (in this example because it starts on C) and a C Major scale starting on the 3rd (E) in the the "accompanying" part.

You can also harmonize in 3rds, which is quite common (and other intervals are possible as well).

For a crash course in 6ths, listen to Brown Eyed Girl by Van Morrison (I know, I know). Soul Man also starts of with some nicely obvious ones.

There is a *pattern* you can learn for 6ths:

Here's a C major scale, harmonized in 6ths, starting with the 3rd on the top and the 5th on the bottom (so G-(C)-E or 2nd inversion of the tonic chord):

--0-1-3-5-7-8-10-12---------------
-------------------------------------
--0-2-4-5-7-9-10-12---------------
--------------------------------------
--------------------------------------
--------------------------------------

If you do this pattern on the 2nd and 4th strings:

--------------------------------------
--0-1-3-5-7-8-10-12---------------
-------------------------------------
--0-2-4-5-7-9-10-12---------------
--------------------------------------
--------------------------------------

You'll have G Major.

The pattern changes on the lower sets of strings - I'll let you work that out.

You may also often start patterns with the root/tonic on top and the 3rd below, so if you started the above pattern on the 8/9 fret you'd be starting with G/B.

Definitely something worth understanding how to use.

Steve