Im kinda new to the whole theory concept, so can someone explain to me the concept of keys?
what are they?
how do you tell what key a song is in?
how do you tell what scales go good with a certain key?
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Every song resolves around a tonal centre, the key of the song. The key of a song depends on the chord progression, root notes, and scales used in the song. If a chord progression is in the key of A, but the lead guitarist starts to solo with C major, it will sound out of place.

You'll have to look inthe lessons section of UG to understand key. I could tell you what chords go with what key, but that's kind of pointless because it won't help you understand it. First, learn about the major scale and chord construction: go to the music theory FAQ sticky. Then, go to this lesson to put the chords in key. Scales go with their corresponding keys. The chord progression helps determine the key. So as you can see, it's all related. A chord progression in A minor can be soloed over with A minor or A minor pentatonic. But you have to start with the basics, the major scale.
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Quote by doctorcheeze200
Im kinda new to the whole theory concept, so can someone explain to me the concept of keys?
what are they?
how do you tell what key a song is in?
how do you tell what scales go good with a certain key?

When someone says that a song is in a certain key, you're being given a set of guidelines, which, if followed, will generally create coherence and a clear sense of tension and resolution. For example, if someone says that a tune is in the key of F major, you're being told your tonal center (home) is F. This means that is F is your ultimate point of resolution. This information also gives you a pool of notes and chords (combinations of notes) to choose from which will sound mostly 'in.' So when we say that a piece is in F major, we're saying F is home, and by using only the notes F-G-A-Bb-C-D-E, we're staying 'in key.'

F is called the tonic, or root, or I of the key. G is called the 2nd or 9th or ii of the key. A is the 3rd or iii of the key. Bb is the 4th or 11th or IV of the key. C is the 5th or V of the key. D is the 6th or 13th or vi of the key. E is the 7th or vii of the key. The way that certain notes are assigned certain numbers is based on the western system of intervals:
0 semitones = unison
1 semitone = minor second
2 semitones = major second/diminished third
3 semitones = minor third/augmented second
4 semitones = major third
5 semitones = perfect fourth/augmented third
6 semitones = tritone/augmented fourth/diminished fifth
7 semitones = perfect fifth
8 semitones = minor sixth/augmented fifth
9 semitones = major sixth/diminished seventh
10 semitones = minor seventh/augmented sixth
11 semitones = major seventh
With some exceptions, you'll most likely be dealing only with the first-named intervals listed in each row. The intervals between the tonic of a major key and the rest of the notes are: unison, major second, major third, perfect fourth, perfect fifth, major sixth, and major seventh.

We say that certain chords belong to the key of F major because of conventions involved in chord construction. The most prevalent system of chord construction is based on stacking intervals of thirds and rearranging the notes to make interesting chord voicings. In the aforementioned key of F major, we have the notes F-G-A-Bb-C-D-E. From these notes alone do we build chords like this:
Start from F. See that the note that is a third above F is A, and include that note in the chord. See that the note a third above A is C, and include that note. So our basic triad (a 3-note chord build by stacking thirds) built from F in the key of F major includes the notes F-A-C. The interval from F to A is a major third, and the interval from F to C is a perfect fifth; these are the intervals of a major triad.

If you want the shortcut to building chords, write out the notes of the key twice on one line. Start on a certain note, skip the next note, include the next one, skip the next one, and include the next one. This will give you the basic triads of the key.
So the chords built in F major are:
F-A-C (F major)
G-Bb-D (G minor)
A-C-E (A minor)
Bb-D-F (Bb major)
C-E-G (C major)
D-F-A (D minor)
E-G-Bb (E diminished)
The intervals of the four basic triads are:
major: unison, major third, perfect fifth
minor: unison, minor third, perfect fifth
diminished: unison, minor third, diminished fifth
augmented: unison, major third, augmented fifth
You'll notice that augmented triads aren't found within major keys. They are found when we look at the different types of minor scales, however, which you can find out about through Google.

We can find the 7th chords of a key by stacking another third on top of the highest note of our triad, so go back and perform the process again. We get the following chords from F major:
F-A-C-E (Fmaj7)
G-Bb-D-F (Gm7)
A-C-E-G (Am7)
Bb-D-F-A (Bbmaj7)
C-E-G-Bb (C7)
D-F-A-C (Dm7)
E-G-Bb-D (Em7b5)

Because the intervals of all major keys are identical relative to the tonic, we can use the above chord-scale to find the chords from any major key that we know the notes of. The tonic is a major triad. The 2nd is a minor triad. The 3rd is a minor triad. The 4th is a major triad. The 5th is a major triad. The 6th is a minor triad. And the 7th is a diminished triad. We can then use this formula to find the chords to another key, like D major. This key contains the notes: D-E-F#-G-A-B-C#. It contains the basic chords: Dmajor-Eminor-F#minor-Gmajor-Amajor-Bminor-C#diminished. Naming conventions for chords let us shorten the names to D-Em-F#m-G-A-Bm-C#*. The asterisk is standing in for the real symbol which is a degree sign.

You can find the key of a song through a few different ways. First, you could analyze the chord progression, seeing which keys it could fit into, and crossing keys off the list, so to speak, when a chord that is played doesn't fit into that key. Listen to what your ears are telling you; they will tell you when a chord progression has resolved. The root of the chord that is played when the progression resolves is probably the tonal center. Second, you could study the melody of the song and perform logical deduction. Remember the intervals of major keys, and if any note is played or sung which doesn't belong to a key, cross it off your list. For example, if G#/Ab is played, you can cross off C major, G major, F major, D major, and Bb major because these keys don't contain G#/Ab. Continue analyzing the melody until you only have one key left, which is the key of the song.

As for scales, if a song is in G major you play G major. If it's in A minor, you play A minor. And so on. It's as simple as that. Don't worry yourself over modes and such until you've internalized all your knowledge of the major scale.

Post any questions you might have, and I'll do my best to explain it better.
known as Jeff when it really matters
It can be tricky sometimes, depending on a song.
Generally a song will have a couple of progressions in them.
Most will have simple progressions or inversions of these progression


example...Sleepwalk and A thousand miles from Nowhere has the same
progression. Different style of music but the same progression.

By using the formula that tito extensively wrote, you use it as a guide
Maj= I,IV,V
min= ii,iii,vi

example..if i see these chords in a song G maj and Amin.
It won't completely define what key it is, but it's been narrowed.

If the chords are Gmaj, Amin, Fmaj...by simple counting, I make out
G is the V chord, therefore the parent scale is in C

If I see Gmaj,Amin,Bmin. I can determind that the Amin is the II, therefore
the parent scale is G

It's tricky somtimes.
If I see Gmaj, Amin, Emin.....it's still not defined.
So...I look at the second progression of that song.
If I see Fmaj then I'll know it's in C as the parent scale.
If I see Dmaj then it's in the key of G as the parent scale.

Another hint is.... sometimes a 7th note is added to the V chord (domiant)
If I see D7..then I generally put that as the V chord....not always but it's usually is the V.
Last edited by Ordinary at Jun 9, 2008,
^Good information, but that covers a lot of ground fast. If you overwhelm him, he'll be more likely to give up. Excellent post though, because it sums everything up perfectly.
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