Name of unusual chords in basic songs

Question

I am a professional musician with a relatively extensive background in music. I also play many different genres of music with people who don't necessarily understand theory. For example, sometimes people will say "play a 2 chord" (we are in the key of G and they want an A chord to be played, which is really a V/v). I understand this, but they don't. I find this one easy to explain so that they know that an A chord is a V/V, and a ii chord would be Am.

What I struggle with is when there are unusual chords and they say play a 3 chord and they want a B7 not a B minor. How do I explain the B7 in a way to make it less confusing to all? ( I was recently in a jam session this past weekend and there was a very long, argument by one member about it. I didn't get involved at all because, I can't give a logical number expanation for that chord in the key of G). What would be the theory explanation for a B7 in the key of G? I could just say V/vi but I don't think that is correct theory, though it would make it less confusing to explain it that way, I think.

Thanks!

Answer 1

The correct term is secondary dominant, i.e. a V(7) for a diatonic chord other than the I chord (as you already suspected). In your example, the B7 is the secondary dominant for Em (the vi chord). The A(7) in your first example is also a secondary dominant, so the explanation/motivation of the B7 chord is in fact identical to the one of the A(7) chord. Secondary dominants are one important source for non-diatonic chords in a given key. In the key of G major you can have the following secondary dominants:

E7  => Am
F#7 => Bm
G7  => C
A7  => D
B7  => Em

Note that a secondary dominant doesn't always need to resolve to its related I chord. E.g., in the key of G major you could also find the progression B7 => C, which would be a deceptive cadence.

Answer 2

I'm focusing on the first question, because I think others have answered the theory part better than I will.

How about just calling it a 'major three'?

Now, before you get out the pitchforks, I know that's not the correct term. Calling it a secondary dominant is better from a theoretical point of view, but if you're playing with people who don't know that theory, it's not going to help.

I think most musicians should know that I, IV and V are major, ii, iii, and vi are minor, and vii is diminished. If you want to specify something different, just say it explicitly- 'major two', 'minor five', etc. Just like you might say 'major flat seven', meaning bVII. Although, I would be likely to just call that a 'flat seven', because 'major' is the default for that particular chord in the styles I play.

There is some potential confusion between 'major three' and 'major third' (i.e., the interval). In context, I don't think that should be an actual problem. Your kilometreage may vary.

Again, this is a pragmatic answer. If everyone understands the appropriate theory, use it. But if it's not working, perhaps pragmatic is better?

Answer 3

A B7 in the key of G is the dominant of the relative minor, e, so V of vi isn't necessarily wrong. It's not an unusual thing to chromatically alter the mediant for this kind of effect, and is an easy way to modulate to the minor, but the context is important to the kind of function it has.

Answer 4

Ok. I'll give it another shot.

Look - the vast majority of musicians don't think in terms of numbers for chords. This has served most musicians well for the last century or so. There are many chords commonly used that do not fall into the simple theory. The B in G is very commonly used and most musicians will know what that means. They will also understand the Bm in G when the time calls for it.

Answer 5

My opinion is that you are thinking too mechanicaly. The 2nd 7th is widely used in any music form. The musical people I know are excited to learn a new use for a chord. This is even true in popular music. Hey Jude used the seventh chord, and people loved it. If you want to look at it technically, it has to do with the minor scale applied to a major key. My point is that you shouldn't discount the chords that are not part of the "official" list. I put that quote in parenthesis because the greatest composers are always trying to break the rules. Just look at the crazy things composers do in classical music, that still sound good.