You already play G7. It is one of the first four, and its shape differs from plain G by a single finger moving two frets down the E string. Play the two back to back and the difference is easy to hear and hard to name: G is content where it is, G7 wants to be somewhere else. One note is doing that. G is G, B and D. G7 keeps all three and adds an F, which is the seventh note of the G scale, lowered by a semitone. Every chord on this page is built by choosing which note to flatten, and this is the first choice.
Hear it before reading further. The two chords below differ by one finger and one note, and the second one will not let you stop on it.
The E string drops from the third fret to the first. That is the whole difference.
If you remember one thing
A plain 7 after a chord name means it leans somewhere. A maj7 means it does not. That is the useful half, and everything below is why it works and what to do with it.
Why it leans
The pull
Two notes, six semitones apart, both of them leaning.
Adding that F puts two notes inside G7 that sit six semitones apart: B and F. Six semitones is the tritone, the one gap in the octave that refuses to settle, and both of its notes have somewhere obvious to go. B sits a semitone under C. F sits a semitone over E. Let them go and you land on C and E, which are two of the three notes in a C chord. G7 does not so much point at C as contain most of it already.
One finger, three chords
The family
Tap along the row. Only the A string moves.
The plain chord. C, E and G.
Adds B, the seventh note of the C scale, untouched.
Flattens that B to B♭, and the chord starts leaning.
Three chords, one finger, one fret at a time. A major seventh keeps the seventh note where the scale left it; a dominant seventh flattens it. That single semitone is the difference between a chord you could rest on and a chord that hands you somewhere to go. The minor sevenths work the same way, flattening the third as well, which is what makes Am7 a minor chord with a seventh on top rather than a different animal.
Build a seventh on every degree of a key and the qualities come out fixed, the same way the plain chords did. In C: major sevenths on the I and the IV, minor sevenths on the ii, the iii and the vi, a half-diminished on the vii that you can leave alone for a few years, and on the V, alone in the whole key, a dominant seventh. That is why G7 carries the meaning it does. It is the only chord in C that sounds like that, so hearing one tells you where you are standing and which way you are facing.
This is also why a Strum Leader can call out a seventh mid-song and nobody needs the chart reprinted. Nine times in ten they mean the one on the V, going home.
In the key of C
- I and IV take a major seventh: Cmaj7, Fmaj7.
- ii, iii and vi take a minor seventh: Dm7, Em7, Am7.
- V takes the dominant: G7, and nothing else in the key does.
Putting one in yourself
When to swap
One is free, one is easy, one changes what the song is doing.
The V is the free one. Anywhere a song hands you G on its way back to C, G7 will do, and most of the room will play it that way whether or not the chart says so. The minor chords take their sevenths too, and one of them costs nothing at all:Am7 is four open strings. Anyone who has picked up a tuned ʻukulele and strummed it without fretting anything has already played it.
The one to think about is your home chord. Putting a dominant seventh on the I, C7 in the key of C, stops it being home and aims it at F instead. That is not a wrong note. It is the opening move of a blues, and songs do it on purpose. Just know you have said it, because the room will follow you there.
Two of the minor sevenths in C. The first asks for no fingers whatsoever.
None of this is homework
A Strum Leader names the chords before each song and shows you any shape you have not met. Knowing why the seventh leans is a bonus, not the price of admission.
Next
The circle of fifths
You know the V wants to go home. The circle shows you why it is the V that does it, and how to move a whole song into a key you can sing.