Scales were invented (discovered?) by Pythagoras.  He figured that whole square of the hypotenuse thing wasn't annoying enough, so just after he went about making playing with shapes a whole lot more complicated with sins and cosins and squares of this and that, he went about complicating learning about music with twelve tones that only have eight names but two modifiers and making sure some of the names and modifiers are completely different but describe the same thing.  At least we don't have to square F#m and then compare it to the sum of the squares of A and Cmaj.   And he used a precursor to a hammer dulcimer to figure this stuff out, so he NEVER had to finger an evil B chord.  And it shows, man.  It shows.

- Zurf

Hey man, we got it easy.  There are eastern music systems out there with 16 and 18 note scales.  Imagine having to deal with quarter tones.

Ook!

Someday I'll figure out that hypotenuse thing.  Then my life will be complete.

weren't scales invented by music teachers to anoy wanna be guitar players,
thanks for your help, i'm starting to get the idea,i'm already starting to transpose songs so as to make it easier for me to sing,where as before i would sing in the key written down regardless of whether it suited me or not.
So it looks like i will a have to learn my scales....dooooohhhhh

Scales were invented (discovered?) by Pythagoras.  He figured that whole square of the hypotenuse thing wasn't annoying enough, so just after he went about making playing with shapes a whole lot more complicated with sins and cosins and squares of this and that, he went about complicating learning about music with twelve tones that only have eight names but two modifiers and making sure some of the names and modifiers are completely different but describe the same thing.  At least we don't have to square F#m and then compare it to the sum of the squares of A and Cmaj.   And he used a precursor to a hammer dulcimer to figure this stuff out, so he NEVER had to finger an evil B chord.  And it shows, man.  It shows.

- Zurf

weren't scales invented by music teachers to anoy wanna be guitar players,

Hah!

It may seem that way at first, but after it clicks, you'll wonder how you ever got along without it. 

Good luck!

How do you know what key a piece of music is in by looking at a set chords for a song.And how do you know which chords to use if you switch keys.

Sorry if this is a bit basic but i have never had a lesson,i just pick up my guitar standard tune it
and play what ever is on the songbook.So if you said play something in "A" i would be clueless

Thanx in advance

Seagull,
   Here's some useful information from some folks who do this music theory/guitar lessons schtuff  for a living. It should be of great help to you. Enjoy.

http://www.ducksdeluxe.com/nashvillenumbersystem.html

Peace and Guitars,
SouthPaw41L

The I IV and V refer to chords named by the 1st, 4th, and 5th notes of a major scale.

G Major scale, for example

G A B C D E F# G

The "in key" chords for this scale would then be

G Am Bm C D em F#dim G

So the I IV and V would be

G C D

Scales scales scales...

So I would say chord progressions originated with the human ear.

There's a lot about music that's very interesting, and it can be found in the study of music theory.

A good rule of thumb is to know the I IV and V's of all keys, which isn't hard to figure out.

For example, if you see a lot of  F, C, and G, you could surmise that the song is in the key of C, as C F and G are the I IV and V of C major.

A study of common chord progressions is also useful in figuring this out.   They call this the "tonal center" of a song.