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.


5 Answers 5


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.

  • 2
    While I wouldn't have a clue what they meant asking for "a 2 chord" I would also not understand what the OP means asking for a V/v. A secondary dominant is the only answer here that makes sense to me. Excellent answer.
    – Doktor Mayhem
    Nov 14, 2016 at 23:24
  • @DoktorMayhem - OP meant V/V - sec.dom. of dom, i.e. A7, often leading to D7.
    – Tim
    Oct 12, 2021 at 11:46

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?

  • "Just like you might say 'flat seven', meaning bVII ". This "analogy" doesn't really work because 'flat seven' refers to the interval (from the root), not to the chord quality. With 'major two' etc. you're trying to describe chord qualities (major or minor).
    – Matt L.
    Nov 15, 2016 at 10:57
  • @MattL I've heard it regularly used to refer to a chord, in the right context. As in, a flat seven, four, one progression to describe G, D, A (in A major). It certainly does refer to the interval in other contexts, though.
    – endorph
    Nov 15, 2016 at 20:13
  • Yes, I agree with that, but the 'flat 7' still doesn't specify the chord type. In that case it usually defaults to a major or dominant seventh, but we can't assume that a beginner knows that. On the other hand, with 'major two' you're trying to make sure everybody knows that they should play a major chord on the second note of the scale. So the correct analogy, in my opinion, would be "major flat 7" (a major chord on the flatted 7th scale degree).
    – Matt L.
    Nov 15, 2016 at 21:43
  • @MattL. For a beginner, I'd be more obvious, but from the question I didn't think the target was a beginner. I've run into many major flat sevens, but I can't remember any minor ones. So, based on the convention of not listing the chord type when it's obvious, I didn't. In the same way, you'd say 'major two', but not 'minor two' (that would be just 'two'). Of course, this depends entirely on the audience.
    – endorph
    Nov 15, 2016 at 22:25
  • With you all the way here. Although if the key is known (here, G), really can't find any reason for not saying, in plain terms 'play A.' Knowing it was actually a 2 (of some sort), means some knowledge of what's going on, but why complicate the issue? Somewhat better than at an audition a long time ago, I asked the bass player what the next key was - he pointed to a fret on a string and said 'this one.'
    – Tim
    Oct 12, 2021 at 11:48

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.


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.


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.

  • 3
    Hey, I'm not sure this answers the question? I think lisa is trying to figure out how to explain the chord quickly to other band members. No-one is suggesting that you can't use such chords; we'd lose a lot of great music if that were true! I've noticed that a lot of your recent answers have similar problems- perhaps try reading over the question a few times, and focus your answer on what you see as the central problem? Other ideas can be left as comments instead.
    – endorph
    Nov 15, 2016 at 2:44
  • @endorph I think this is the best explanation, honestly. Trying to explain how an arbitrary bit of music follows overly-specific and overly-simplified rules is the wrong approach and they should think about it differently.
    – user28
    Nov 15, 2016 at 15:18
  • 1
    @MatthewRead Certainly, I think the question is overtheoreticised. But you still need to be able to describe the chord to another player, which is the point of the question. This answer doesn't cover that at all. I was trying to nicely point that out.
    – endorph
    Nov 15, 2016 at 20:18
  • I'm in agreement with endorph. This doesn't address the question of how to explain and name a chord that actually is a secondary dominant, to someone with less knowledge. All it says is 'think differently' - but fails to explain how. -1 from me. A rarity.
    – Tim
    Nov 16, 2016 at 8:20
  • The way I was seeing the question is that the poster was B7th was not an 'official' part of the key of G. That is just ludicrous. That chord is used all the time.
    – Marc Perry
    Nov 21, 2016 at 11:27

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.