# Blues question

BarryS
Member
Joined: 07/06/00
Posts: 75
11/20/2000 12:13 am
I've been wondering this for a while. What is meant by the I-IV-V blues progression? I know it has something to do with the 12 bar blues form, but where does the I, IV, V come from?

Thanks.
LuigiCabrini
Senior Member
Joined: 06/23/00
Posts: 207
11/20/2000 12:57 am
It comes from the roman numeral chord designation system. Let's say we're in the key of A (a common blues key.) Each chord can be represented by a roman numeral
I ii iii IV V vi vii
A B# C# D E F# G#

The upper or lower case refers to the quality of the third in the chord, upper case = major third, lower case = minor third.

In a standard blues progression--one without any substitutions or additions or anything that is often done to blues to make it more jazzy--there are only 3 chords used. In any key, they are the I, IV, and V chords. In the key of A, the I, IV, and V are A, D, and E. A side note, they are all dominant chords but they don't provide a dominant function. What I mean is that they have the maj3 and min7 that makes them by definition dominant, but they don't always resolve to a I. (The function of a dominant chord is to pull back to a tonic chord, they aren't being used that way in blues.)
Anyway, to simplify, a basic 12 bar blues, in any key goes like this:
I I I I
IV IV I I
V IV I V
As you can see the only chords are the I, IV, and V. This system is helpful because it can be applied to any key, just find out what the I, IV, and V of that key are and plug in. Incidentally, this can be used to describe all chord progressions that have some relation to key (don't try using this to describe giant steps) and it is a helpful tool for explaining chord progressions.
BarryS
Member
Joined: 07/06/00
Posts: 75
11/20/2000 5:53 am
Thanks, dude. Damn, you sure know a lot of theory stuff.

So, a 12-bar blues progression in A would go like this:

A, A, A, A, D, D, A, A, E, D, A, E. Right?

How do you find out what the I, IV, V chords are? Like if I wanted to know the I-IV-V chords for the key of E?
LuigiCabrini
Senior Member
Joined: 06/23/00
Posts: 207
11/20/2000 11:53 am
That's right in A, in E, just use the same method.
I ii ii IV V vi vii
E F# G# A B C# D#

The I is E, the IV is A, and the V is B. All you have to to is count from the root chord of the key (Think E=1, count 1 2 3 4, then 1 2 3 4 5 to find the I, IV, and V chords, making sure that they have appropriate sharps or flats depending on key sig.)
So the 12 bar would go
E E E E
A A E E
B A E B
Keeping in mind that sometimes the last bar is E, and sometimes the second bar is A, and there are lots of other possible substitutions, but that's the basis.
John O'Carroll
Senior Member
Joined: 04/13/00
Posts: 173
11/20/2000 2:15 pm
You've probbably figured this out already but here are the
"I-IV-V"s:

A-D-E
B-E-F#
C-F-G
D-G-A
E-A-B
F-Bb-C
G-C-D
A#(Bb) - D#(Eb) - F
C#(Db) - F#(Gb) - G#(Ab)
D#(Eb) - G#(Ab) - A#(Bb)
F#(Gb) - B - C#(Db)
G#(Ab) - C#(Db) -D#(Eb)

Now you can play I-IV-V blues in any key you like. This comes in handy when a singer requires a flat or sharp key for their accompanyng music. This can also be accomplished with a capo - guitar, such a versatile instrument.

[Edited by John O'Carroll on 11-20-2000 at 09:18 AM]