Look at What's In Your Chords

Consider, for a second, the common, closed D chord.  Four fingers, four notes.  What are they?

Index finger: F# .  Second fret on the E string.  Middle finger: F#.  Fourth fret on the D string.  Octaves. They rhyme.

The third and fourth fingers?   Ring finger, fifth fret, A string: D.  Pinky, seventh fret, G string: D.  Another rhyme.

Two D's and two F#s.  At the risk of getting all music-theory-ish on you, chords have three notes -- root, third, and fifth.  This one has two roots and two thirds.  No fifth.  The other instruments are covering the last one.  There's a reason you brought along a guitar player.

But couldn't those two notes be something else?  Without that last note of the chord, isn't there some ambiguity?

What are the possibilities?  Let's work it through.  Could F# be the root?  F, G, A, B, C, D ... 1, 2, 3, 4, 5, 6.  The D would be the sixth, so it could be an F#6 maybe.  Not very Appalachian but okay, it could be that.

One more possibility: could F# be the fifth?  5, 4, 3, 2, 1 ... F, E, D, C, B.  Could it be a B chord with the D as a third?  A missing root?  Hmm.

Let's look more closely.

We could do this from where we are but, believe it or not, it'll be easier to work through if we slide the whole chord up one fret, to make it an E-flat.  Each finger goes up a half a step.  Bear with me here.

Our two notes were F# and D,  Now, they're G and Eb, and we're asking if these could be the fifth and third of ... let's see ... G, F, E, D, C: 5, 4, 3, 2, 1.  Is this a C chord?

(C's pretty easy to think about.  That's why we slid up a fret.)

A C major chord is C/E/G.  The e-flat turns it into a C minor. If you have some other musician around, play this D-shape-slid-up-fret while he plays a C minor, and you'll hear it.  Sure enough. You have a C minor.

Well, now.  If that's a C minor, then sliding it back down a fret to where you started must give you a B minor.  B minor is a useful chord because it's the relative minor of D, which means that it shows up in D tunes more often than any other minor chord.  Your guitar or piano player may decide to throw some in because they sound good.  What do you do when that happens?  You may move to some other shape on some other fret, but you don't have to.

Three-note chords are another story.  D major is D/F#/A.  B minor is D/F#/B.  Big difference.  Without that last note, though, the shape can be either chord.

Let the rest of your band do all the work. You can just stay right where you are.

Suppose staying where you are isn't an option.  Scotty has forced you into the transporter room of the Starship Enterprise and beamed you up into the middle of a Klezmer jam.  They're playing in D Freygish.  The three chords aren't D, G, and A, they're D, G minor, and C minor.  You already know how to play the D's.  The C minors?  Just slide it up one fret!

The G minor?  You're on your own.  You know there must be several options, but for starters you can fall back on the Universal Chord.  You have, after all, two of the three chords, and you only have one left to bluff your way through. You'll find some shape that'll work for the G minor during the break, while the clarinet player and cimbalom player squabble about what tune to play next.

Oy vey.