Chord progressions and key

Question

I'm trying to deconstruct a song written in CMin (according to a website).

I know how to find the notes within a key and have been able to transcribe a few lead riffs but the chords seem weird to me; would it be a proper to assume that all of the chords in the song are written in the CMin (so I could simply use a trial and error approach till I get it right, sounding well)? Or do these key changes change the overall song key?

Is there an overall song key and within that sub keys throughout the song?

If I play a CMaj sustained, I know I can noodle around on the CMaj keys and it will sound good. But if I then play a DMaj chord (which adds C# and F#), am I now playing in the key of DMaj?) If I played a DMin chord though (which is found in the CMaj key), am I still in CMaj or have I now changed to the key of DMin?

Am I making any sort of sense?

Answer 1

Most songs are built within a key, however it is not uncommon to have chords outside the key in a song. There are several ways to incorporate chords outside the key including:

• secondary dominants
• Substitutions
• Borrowing
• Chromatic

With all the above examples you are still in the key you started in, just the harmony is temporarily not reflecting the key. Typically the melody you play would also reflect this change.

There are times when there is a departure from the current key and that is known as a modulation. It's not extremely common in modern music, but you will encounter it.

I'll address your example, but modify it slightly to a more typical example. If you play the chords CMaj7 - D7 - G7 - CMaj7 you are still in C major. The D7 is not naturally in the key of C major, but is acting as a secondary dominant to the G7. When you play the D7 then you would want to play the notes of the G major scale to reflect this departue, but once you get to the G7 you would want to play C major again. You never changed keys, but the G major scale makes more sense to play over a D7 then a C major scale. Pretty much if the chord you are playing is within the key, you can just play the scale if not however you have to think about what the chord is and what makes sense to play over it.