Remedial Music Theory: What's a "+" chord?

When a chord is written as


what does this mean?

(The appearance that currently has me troubled is not accompanied by any notation- otherwise I’d everygoodboydoesfine it out for myself. Also, I ain’t about to try a search for “+”.)

I’m certain I’ve encountered such chords before, but accompanied by a chord chart so that I just learned the formation without really understanding what it was.

So, first off, what’s the chord called? And how do you build one?

It’s an augmented chord: a triad with the fifth raised a half step.

For example, C+ (or C aug) is C E G#.

Thanks Biffy! I can do that!

*bien Dusting off those Steely Dan charts?

While we’re on the subject, how about diminished, sixth, and seventh chords?

My impression is, working with the C chord as base, and using a small “b” for the “flat” sign:

Cdim = C, Eb, Gb, A

C sixth = C E G A

C seventh = C E G Bb

Is that correct?

IIRC, a cool thing about the augmented chord is that it’s moveable on a guitar, assuming that you are using a fully-fingered inversion–i.e., no open strings. I don’t remember what the interval is, but if you move an augmented chord up or down the neck by that interval, you will wind up with an inversion of the same chord, without having to change the fingering.

*Biffy, is the interval a fourth? I don’t remember.

That’s the diminished 7th chord, usually indicated in jazz charts as C°. There’s also the half-diminished chord:

C Eb Gb Bb

…sometimes written as above with a horizontal or diagonal slash through the circle, and other times as Cm7b5 or C-7b5 (where the “-” indicates minor).

It’s a major third. The augmented triad is itself two stacked major thirds; if you go up another major third you return to the root. So there are really only four augmented chords:

C E G# (= C+ root position, E+ second inversion, or G#+ first inversion)
Db F A
D F# A#
Eb G B

…after that you start repeating the same combinations of notes.

Being a guitar player, yes, the augmented chord, when moved four frets upward or downward becomes the same augmented chord.
The *diminished chord * requires only a 3 fret jump to become the same chord.

Just to clarify, a fourth is not the same as four frets. Four frets is a major third, three frets is a minor third, and five frets is a fourth.

Pretty much right. A plain vanilla Cdim is only C, Eb, and Gb, though. You can usually add the diminished 7th (A) on top of it.

C7 is, as you said, C E G Bb. It’s also known as the dominant seventh chord. You also have the major seventh which is C E G B. It is notated either as Cmaj7 or C[symbol]D[/symbol]7.

Then, of course, there’s the minor versions of these chords.

Cm6: C Eb G A
Cm7: C Eb G Bb.
CmMaj7: C Eb G B.