12-bar blues...

Hi guys...I was wondering what is exactly meant by '12-bar blues'. I think I know the 'blues' part, but what about '12-bar'? Is it a term applicable to other musical styles, or just unique to blues? Thanks :)

A bar, is to do with the timing. Say it's 4/4 timing, then four beats is one bar. So 12 bars is 12 sets of 4 beats. As for the 12 bar blues, it's just a standard blues progression that lasts 12 bars. I'm not sure why it's 12 exaclty, but all it is that the piece of music lasts for 12 bars before repeating or ending. Not the best of explanations, one o the other guys can probably do better.

"bar" is just a slang term for measure. So all 12 bar blues means is a blues that is 12 measures long in form, this is the most common.
There is also an 8 bar blues form and a 16bar blues form. All other forms are mainly variations of these (24 bar blues & 32 bar blues).

A 12 bar blues is generally a I, IV, V pattern, which generally goes something like this (with each chord representing one bar):
I, I (or IV), I, I,
IV, IV, I, I,
V, IV, I, I (or V)
As you can see, there are twelve bars, that you can repeat for as long as you like. The twelve bars form one "verse".

http://www.guitarnoise.com/beginner/20010205.html

nails it down quite solidly..










(have to go back occasionally-- past experiences of playing 46.25 bar boogies under the *cough* influence have...varied the ol timing)