I'm trying to understand chord construction, but have hit a rut. How can you play minor chords that will put you out of key?

This is my current conundrum:
I'm playing in G Major. I should use minor chord shapes for B, but

B minor (as in I bIII V) would be a B, a flat D, and an F#, correct? A flat D is C#; totally out of key for G Major.

What am I doing wrong?
A B minor triad is the notes B D and F#, not B Db F#. A B major triad is B D# F#. Where did you get the D flat? The chord B - Db - F# would actually be spelled B - C# - F# and it's a Bsus2 chord.

Bminor is the iii in the key of G. you're progression is a I - iii - V. If you're sticking with the susiii then it's I - iiisus2 - V.
Last edited by macashmack at Jul 8, 2014,
I was using the formula I found here: http://www.guitarlessonworld.com/lessons/chord-construction.htm for a minor chord, because in G Major you play maj, min, min, maj, maj, min, dim. I guess I still don't fully understand what I'm doing. Why wouldn't I follow the I bIII V formula creating all minor chords? Does the minor formula only apply if I'm actually playing in a minor key?
Quote by 'xander vasil
Why wouldn't I follow the I bIII V formula creating all minor chords?

B D F# is the 1, b3 and 5. You are following that pattern. THe distance between a B note and a D note is a minor third.

Count it out in semitones. A minor third is three semitones, right? So B to C is one semitone. B to C# is two semitones. B to D is three semitones.

I think you're getting confused because you're thinking "okay, a flat three ... so B to D is a third, flatten it to get to Db," but B to D is already a minor third. Where G to B, for example, is also a third but it's a major third, four semitones.
The minor third of a B is D, not Db.
Semitones! Now my whole world makes a lot more sense! Thanks a lot, guys.
Understanding chord construction is much easier if you have a good grasp on intervals first...

Here's a couple of posts that were written to explain intervals in some detail.
Intervals part 1
Intervals part 2
Si
Quote by 'xander vasil
B minor (as in I bIII V) would be a B, a flat D, and an F#, correct? A flat D is C#; totally out of key for G Major.

What am I doing wrong?

Mac already explained how Bminor actually contains a D (not flat or sharp), not a Db. But I want to hone in on the bold part...

You will see a lot of chord progressions that "borrow" a major or minor chord from another key. These chords are referred as non-diatonic. A diatonic chord is built strictly from the notes of the key signature.

So, the key signature of Gmajor is: G, A, B, C, D, E, & F#. As such, the diatonic chord of the key of Gmajor are: Gmaj, Amin, Bmin, Cmaj, Dmaj, Emin, & F#dim. These chords all contain the notes of the key signature.

Ok...now, back to the Bminor chord. We borrowed that chord from the relative minor of Gmajor, which is Eminor. (The notes of Eminor are E, F#, G, A, B, C, & D. Notice that the notes are the same, BUT the tonic [read: "home note"] is different.) This is a fairly common thing, borrowing chords from another key.
Quote by crazysam23_Atax

Ok...now, back to the Bminor chord. We borrowed that chord from the relative minor of Gmajor, which is Eminor. (The notes of Eminor are E, F#, G, A, B, C, & D. Notice that the notes are the same, BUT the tonic [read: "home note"] is different.) This is a fairly common thing, borrowing chords from another key.

Bmin isn't borrowed from E minor. It's in G major all on its own.

An example of borrowing would be playing a Bb major in G major, which is borrowed from G minor.