How do you know what key a song or a solo is in?

What does the key of a song mean?

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you can usually find the key of a song by the first chord, uhhh as for what a key is...well I'm not 100% sure how to explain it to somebody who doesn't know much theory so, a key is just like with a scale, you get the root from the (on the major scale at least) first note....eh I'm sure someone can explain it much better.

So like with a C major scale you have: C D E F G A B so a chord progression with C D E would be in the key of C....if my small (but ever expanding) knowledge of music theory is correct

DISCLAIMER: I may just be an idiot who has no idea what he is talking about
Last edited by hendrixism at Feb 22, 2009,

Not neccesarily <(I miss FF stupid new computer). You could start a song with a chord other then C and still have it be in the key of C.

From what I know + quoting because I'm lazy.

Often, the "root" chord is either the first or last chord in a chord progression. For example, in the 12-bar I-IV-V progression (see Chapter I-3) I made for you, the first chord (A Major) is the root... In other progressions, the last chord in the progression is the root. A better general rule is: the chord that "resolves" the progression best is the root chord. For example, in the "Knocking on Heaven's Door" video, the last chord played is F# Major, and this chord "resolves" the progression...

A better way to determine the key of a song, however, is to look at ALL the chords in the progression, and trying to fit them in a certain harmonized scale. For example, "Knocking on Heaven's Door" has a B Major and a C# Major in it. These are 2 Major chords that are 2 semitones apart... That means, they HAVE to be chords IV and V of the harmonized scale, because that's the only place in the scale where 2 Major chords are adjacent! So, if B Major is IV, just count backwards (5 semitones) and you'll find that F# Major is the root note... You can use "orientation points" like this in other progressions as well to determine the key, it just takes a little puzzling!

This is a better way of determining the key of a song, because it takes less "guesswork". However, it's not always possible to determine the key of a song with a 100% certainty using this method... For example, some songs use chord progressions with only 2 chords, without even using the root chord. This makes determining the key even harder!

Like I said, determining the key of a song takes some getting used to. In many cases, you're not able to say right away what key a song is in. This is made even more difficult by the fact that Major scales have their relative Minors! For example, Eric Clapton's "Layla" (unplugged version) uses a Dm-Bb-C progression in the chorus. Bb and C are, again, adjacent Major chords, which would lead you to the conclusion that the song is in F Major (Bb and C being chords IV and V in F Major harmonized!). However, in this case it's more logical that the key is D Minor, the relative Minor scale of F Major, simply because there's no F chord in the progression, but there is a Dm chord.


That helped me a bit.