Sounds like you want to know the difference between a Major Key and a Minor Key, why they are relatve, and why they are different....


While the I-IV-V chord of a Major Key all Major chords...they are not all Minor chord in a Minor Key.

The reason being is the the V chord HAS to have a leading tone of a Cadence(a M3 of the V chord moving a half-step to the Root of the Im chord).

So a song in the Key of C Minor would have i-iv-V or Cm-Fm-G7.

Think about it this way...

You probably know about Relative Minors...How the C Major scale and the A Minor scale are related...

Looking through a sheet of music, a song with a Key Signature of no sharps or flats is the Key of C Major, right? But, relatively it could be the Key of A Minor, right?

Well, what makes it the Key of C Major or the Key of A Minor?

In either of those Keys you have C D E F G A B C, right? So what's the difference?

How you find out which your dealing with is, you look through the sheet to find ANY accidentals. If you find a G# note (which would be the M3 of the V chord in the Key of A Minor) it's a good indication that it's the Key of A Minor and not C Major.

It's the cadence (M7 to Root resolution) that determines the Major or Relative Minor Key.

IOW, the V chord has to have a M3 note in it to resolve a half-step higher to the Root of the I chord...be it a I or a Im. In a nutshell...the V chord HAS TO BE Major and resolve to a I or a Im chord.

Try it, play (and make sure you repeat because the V chord to the I chord is where it should resolve):

||: Am | Am | Dm | Dm | Em | Em :||

Kind of flat sounding, nothing telling it Cm is DEFINTELY the Im chord. No strong cadence from the Em back to the Am.

Now try (and make sure you repeat!):

||: Am | Am | Dm | Dm | E | E :||

You should hear the final movement of the M3 (G#) in the E chord moving to the Root (A) of the Am chord.

The second progression is in the Key of A Minor. The first progression is technically still in the Key of C Major.

So, any music that has an accidental of the M7 of the Relative Minor chord is in the Relative Minor Key as opposed to the original Major Key.

Scale wise...

The Minor scale has R 2 b3 4 5 b6 b7 R (For A Minor: A B C D E F G A)

There is NO G# in the A Minor scale.

So to get this cadence, leading tone, or strong resolution...you can look at either the A Harmonic Minor scale or the A Melodic Minor scale. Preferrably the A Harmonic Minor scale for right now.

How does this all pan out, or why, or when do you use the A Harm Min?

The Harm Min has these Intervals: R 2 b3 4 5 b6 M7 R (A Harm Min: A B C D E F G# A)

Look that scale has EVERY note n the A Minor scale but replaces the b7 with the M7, or the G# note, the M7 of the Am chord.

So, now look at that progression in the Key of A Minor again:

||: Am | Am | Dm | Dm | E | E :||

For the Am and Dm chords, just play around with the A Minor scale, but for the E chord play A Harm Min over it!

You'll hear a COMMON resolution that's been used for centuries. You'll hear how the Harm Min scale resolves to the A Minor scale just as you did the E chord resolving to the Am chord.

All in all a Major Key is a Key using the Major scale, but a Minor Key is a Key using the Natural Minor, Harmonic Minor, and/or Melodic Minor scale.

Hopefully this will help you see how a Major and Relative Minor Key aren't really exactly the same. But, you'll be able to dechiper when you're dealing with one or the other.