What scale are the chords Em A C D in?

Question

I've been trying to work out what scale a song with chords Em A C D is in.

The major chords A, C, D are never together in any scale. If C and D are there it would suggest the key is G but then the A would be minor. How is it possible the song can have these chords and in what scale is it?

Edit: Later in the song the A major sounds more like Asus2.

Edit: As an example this is a song that has this chord progression

Answer 1

Your question is based on a misunderstanding, which is "there must be a single scale fitting a chord progression". This is usually wrong; many interesting chord progressions are not based on the notes of a single scale. The chords in your progression have a C (C major) and a C# (A major), which, as you've noted, usually don't occur in the same scale.

There are two ways to get around this when playing a melody / improvising over such a progression. Either you skip the "dangerous" notes; i.e., you avoid both the C and the C#. This will leave you with an E minor pentatonic scale, maybe with an added F# (i.e., an E natural minor scale without the sixth note). The other option is to use both the C and the C#, but only where they fit the chords, i.e., use a C over C major, and a C# over A major.

Most people will hear this progression in the key of E minor. Note that the key of E minor is not a single scale, but the union of E natural minor, E harmonic minor, and E melodic minor. And in this way the C as well as the C# become available; the same is true for the D and the D#; the latter doesn't occur in your progression, but it could; try:

|| Em | A | C | D B7 ||

To most ears this would sound as a perfectly conventional progression, and its chords contain a C, a C#, a D, and a D#.

For more information on minor key harmony have a look at this post.

Answer 2

As Matt L. said, this is pretty clearly E minor (natural minor, i.e. Aeolian mode). The A chord can be understood as a borrowed chord from the nearby Dorian mode:

X:1
L:1/4
M:
K:C
V:2 clef=treble name="Aeolian"
e, ^f, g, a, b, c d e "C (VI)"[e, g, c]
V:1 clef=treble name="Dorian"
e, ^f, g, a, b, ^c d e "A (IV)"[a, ^c e]
%

This major IV degree in a minor mode is an extremely common borrowed chord. A great example is Stairway To Heaven, where it is used both to convey a sort of folky mood (Dorian and Mixolydian scales tend to sound a bit celtic on guitar IMO), and to weave in chromatically descending lines.

X:1
L:1/8
M:2/4
K:Am
V:1 clef=treble-8
"III"[g,c']ecc' | "IV"[^f,^f]da,^f | "VI"[f,e]ca,c
%

Answer 3

Your question is based on a misunderstanding, which is "there must be a single scale fitting a chord progression - Matt L.

I would agree, but just in case you actually search a scale that fits all notes combined from Em, A, C and D, you could go Bebop:

• D Dominant Bebop: interval set 0-2-4-5-7-9-10-11 scale: D E F# G A B C C#/Db
• A Minor Bebop: interval set 0-2-3-4-5-7-9-10 scale: A B C C#/Db D E F# G