Chord Transposition for the Guitarist:

A useful skill for the guitarist (or any musician for that matter) is the ability to change the key of the song you are playing. One option on the guitar (which some of you have discovered) is the use of a capo. A capo allows you to continue to play the same chords you "memorized", but changes the key depending on the placement of the capo. This is a viable option in some cases but it also changes the tone considerably if you are moving more than just a couple of frets. Another option might be an alternate tuning. Again, a viable option if you want to move the key by a half or whole step. Beyond that you are going to run into all sorts of problems.

This brings me to the point of this post:

Understanding transposition will help you out when those other options are either not appropriate or unavailable (hey, I forgot my capo!)

Let's take a simple chord progression in the key of G:

G-C-G-D

Perfect. Simple, a few primary chords. We'll we need to understand the relationship of the chords to the key and each other. We do that by thinking of the key of G and numbering the notes of the scale (these numbers will also correspond to the chords we build on those scale degrees).

G-A-B- C- D-E- F#-G

 I- ii-iii-IV-V-vi-vii- I

You will notice that I am using Roman numerals. These are the standard for music analysis. They are helpful because they have an uppercase and lowercase. Uppercase for Major and lowercase for minor.

Let's look ate that chord progression again with Roman numerals...

G-C-G-D

I- IV-I-V

Once I know the chord numbers, I can move them to any key I want.

Observe...

The Key of A

A-D-A-E

I- IV-I-V

The Key of D

D-G-D-A

I-IV- I- V

Here is a Handy Chart of Keys and how they notes and chords in those keys are related:

I	ii	iii	IV	V	vi	vii	I
C	D	E	F	G	A	B	C
F	G	A	Bb	C	D	E	F
G	A	B	C	D	E	F#	G
D	E	F#	G	A	B	C#	D
A	B	C#	D	E	F#	G#	A
E	F#	G#	A	B	C#	D#	E
B	C#	D#	E	F#	G#	A#	B
Bb	C	D	Eb	F	G	A	Bb
Eb	F	G	Ab	Bb	C	D	Eb
Ab	Bb	C	Db	Eb	F	G	Ab
Db	Eb	F	Gb	Ab	Bb	C	Db

Remember, uppercase Roman numerals represent Major Chords and lowercase represents minor Chords. If the the chord is a 7th, you can add that next to the number as well.