Music Theory question

[graeme75]

Hi

I have been following a tutorial that is in B major key and only has 3 chords. Those chords are B maj, F#sus4 and A maj. The melody is then created from the notes in these chords

What I don’t understand is that A maj is not a chord in the B maj scale (g# and a# are) so how does it not sound out of place?

Any help greatly appreciated

Cheers
Graeme

[Timmy Crowne]

The Amaj can be derived from the parallel key, B Minor. It would be based on the 7th degree of that scale. Chords from parallel keys can often be borrowed and used in a given progression. It’s also noteworthy that the F#sus4 could be in either B Major or B Minor because its 3rd is suspended. So in this case it can serve as kind of a bridge to the B Minor scale.

Of course, some chord progressions can’t be explained theoretically. Why something sounds good can’t always be rationalized this way, but analyzing it like this can be useful if it opens the ear to other possibilities.

[bossa]

The A maj chord can be explained as a "modal interchange". Please see this wonderful youtube video:

[Yonatan]

B maj - F#sus4 - A maj - (E?).

All said above about B and Bm as parallel and modal interchange is true.

"The Circle of fifth" is your best friend here. Would make it a bit more visual than me writing.
You can see that A major is the 4th and subdominant chord in the key scale of E, and E in turn is the 4th and subdominant in the key scale of B. The circle of fifth moves counter clockwise and clockwise by 7 half notes, the 4th (subdominant) is at each counter clockwise and the and clockwise has the 5th (dominant). For example B has E as subdominant counter clockwise and #F (or Gb) as dominant clockwise.
B is the 5th and dominant chord in the key of E. So all those interconnections are making us accept it very naturally as we are not only so trained to these co-relations by ear, but it is logical in our most common classical musical system.

Try go from A major chord to E major chord and you will suddenly feel that E could have been the main key all along but not starting at home, just ending there. As A major is the subdominant in the key of E, it is a bit more subtle and not the total "home" as from a 5th so you still can claim to be in the key of B, it just depends on where to go next from there (the context).