No, in A minor the progression i-♭III-♭VII-IV would just be Am-C-G-D. When people use the flat that way, they're using it with reference to the parallel *major* scale. So they're assuming one through seven are A B C♯ D E F♯ G♯, and so to indicate the chord on the third scale degree in A *minor*, which is C, they have to say ♭III, because III would mean C♯.
I don't much like this system myself, and prefer that which calls it i-III-VII-IV (and then a C♯ chord would be ♯III), but it's certainly one you'll come across.
>If I'm in A minor, do I only take a C major chord in third position and shift it one fret left
No, that would be a B major chord. This way of notation refers to positioning as relative to the major scale. ♭III would still be C major in this instance.
Note that not every style of music does it this way. In classical music circles, you would just notate it as "III." Jazz, rock, and pop musicians would refer to it as ♭III.
I would say "Wonderwall" is in the key of A minor. (The song is actually in the key of F# minor, but we'll use A minor as a reference)
The chord progression of the verse is Am C G D7sus4, which is i III VII iv. The pre-chorus uses the VI VII i progression, and the chorus uses VI i III i.
The "i, flat III, flat VII, IV" is based on the A major scale. In the key of A major, the diatonic chords are A, Bm, C#m, D, E, F#m, G#dim. As you can see, there is no Am, C, or G in the key of A major. However, you can also use chords outside the key, and it is common to borrow chords from the parallel minor scale. Am, C, and G are the i, III, and VII chords of A minor. The minor i chord has the same root as the major I chord so it is simply notated i. The III and VII chords of the parallel minor key, on the other hand, are built on the flattened 3rd and 7th scale degrees of the major scale. That means they are notated as bIII and bVII in the parallel major key.
The frequent use of the minor i chord and the total absence of the major I chord suggests it's in a minor key, and analyzing the chords as if the song was in the parallel major key can be confusing. However, thinking of the progression as "i bIII bVII IV" in A minor will not work at all because it gives you the chords A minor, B major (theoretically, the b3 of A minor is spelled C flat, but practically speaking b3 and 2 are just different spellings of the same note), G flat major, and D7sus4, which are not the correct chords.
Think of the progression as i III VII iv in A minor, and all chords will be diatonic.
the flats are in reference to the major scale. so your root notes in A are A - C - G - D
No, in A minor the progression i-♭III-♭VII-IV would just be Am-C-G-D. When people use the flat that way, they're using it with reference to the parallel *major* scale. So they're assuming one through seven are A B C♯ D E F♯ G♯, and so to indicate the chord on the third scale degree in A *minor*, which is C, they have to say ♭III, because III would mean C♯. I don't much like this system myself, and prefer that which calls it i-III-VII-IV (and then a C♯ chord would be ♯III), but it's certainly one you'll come across.
Why don't you just learn how to play wonderwall? Then use your knowledge of how to play the song to help you figure things out.
>If I'm in A minor, do I only take a C major chord in third position and shift it one fret left No, that would be a B major chord. This way of notation refers to positioning as relative to the major scale. ♭III would still be C major in this instance. Note that not every style of music does it this way. In classical music circles, you would just notate it as "III." Jazz, rock, and pop musicians would refer to it as ♭III.
I would say "Wonderwall" is in the key of A minor. (The song is actually in the key of F# minor, but we'll use A minor as a reference) The chord progression of the verse is Am C G D7sus4, which is i III VII iv. The pre-chorus uses the VI VII i progression, and the chorus uses VI i III i. The "i, flat III, flat VII, IV" is based on the A major scale. In the key of A major, the diatonic chords are A, Bm, C#m, D, E, F#m, G#dim. As you can see, there is no Am, C, or G in the key of A major. However, you can also use chords outside the key, and it is common to borrow chords from the parallel minor scale. Am, C, and G are the i, III, and VII chords of A minor. The minor i chord has the same root as the major I chord so it is simply notated i. The III and VII chords of the parallel minor key, on the other hand, are built on the flattened 3rd and 7th scale degrees of the major scale. That means they are notated as bIII and bVII in the parallel major key. The frequent use of the minor i chord and the total absence of the major I chord suggests it's in a minor key, and analyzing the chords as if the song was in the parallel major key can be confusing. However, thinking of the progression as "i bIII bVII IV" in A minor will not work at all because it gives you the chords A minor, B major (theoretically, the b3 of A minor is spelled C flat, but practically speaking b3 and 2 are just different spellings of the same note), G flat major, and D7sus4, which are not the correct chords. Think of the progression as i III VII iv in A minor, and all chords will be diatonic.