When the Sheet Music says D, however, the notes of a D scale include a C# and the song has a C in the chord progression how does one understand how to communicate to your band what key the song is in?
Diatonically its spells out G major. But this is not what the ear hears. The ear hears a pull to D. How’s that possible? Let’s take a deeper look.
How could such a simple 3 chord progression cause so much confusion? Let’s take Sweet Child of Mine by GNR. Starts off with a ( D – C – G – D). To a lazy theorist, this seems like it’s all in the Key of G Major. But upon further investigation, this is not the whole story.
If we analyzed the song in G, the Roman Numerals would be V IV I V. Yes, All the notes would fit, but playing a G Ionian mode from G to G doesn’t quite fit the tonality closely enough.
Now let analyze the song in D Major. But wait, you say there is a C# in D and there exists a C in the Chord Progression. This stumped me a bit as well. But on further inquiry, I have found the answer.
If we analyze this in Roman Numerals, we get an ( I – b7 – 4 – 1 ) progression in D Major. Wait? That doesn’t exist in any Diatonic key chord progression. But yet in rock and roll music, it is fairly common so there must be an answer as to why it sounds like it is resolving to D.
If you said it’s a Plagal Cadence congratulations you are a not a lazy theorist. It definitely is a Plagal Cadence. ( IV – I )
But then how the heck can you explain the Flatted C chord or the b7?
According to my sources, it is considered a double Plagal Cadence. This is something I have not yet come across although I have been playing the song for 20 years. I believed it was in G Major my whole life. Why not?
After All, the notes of G Major do fit properly over the chords. But it doesn’t resolve to G, it resolves to D. And the answer to the 10 million dollar question is this:
The C Chord is an ( IV/IV ) which in English means it’s a 4 of a 4 chord. So to re-analyze correctly in the key of D. We have an ( I – IV/IV – IV – I ) progression. A simple way to look at this is that in Rock music a b7 is so similar to a #7 in the strictest sense of the key. So, in Rock Music, a b7 can be a substitution in for a #7 at any time without affecting the key signature.
Therefore to solo over this progression, one simple answer would be to use the D Mixolydian Mode. From D to D it contains the following notes ( D, E, F#, G, A, B, C ).
Most importantly the ear should be the final say in these situations and you can hear the song pulling to the D.
Enjoy the song in a new light if you haven’t already. To me. It’s one of the coolest songs ever written.
So what key is Lynrd Skynrd’s “Sweet Home Alabama in?” Lol