Open Chords in Fourths

Fourths tuning has different open strings than standard (E-A-D-G-C-F instead of E-A-D-G-B-E). The top two strings - C and F - create chord voicings that do not exist in standard tuning. These open shapes are comfortable, resonant, and worth memorizing.

Open String Triads

The six open strings (E-A-D-G-C-F) contain the notes of several common chords. Here are triads built entirely or mostly from open strings.

C major uses three open strings: E (3rd), G (5th), C (root). F major uses A (3rd), C (5th), and F (root). A minor and D minor also fall naturally across the open strings. No barre required.

The Am7 Gift

This is the signature open chord of P4 tuning. A minor 7 (A-C-E-G) uses four open strings. Every note is a chord tone. It sounds full and requires zero effort.

E (5th), A (root), G (b7), C (b3) - all four notes of Am7 on open strings. This voicing is impossible in standard tuning.

Open Chords with Fretted Notes

Add one or two fretted notes to the open strings for richer voicings. These shapes take advantage of the open C and F strings as chord tones.

The C major shape puts the root in the bass: A string fret 3 = C (root), D string fret 2 = E (3rd), G open (5th), C open (root). The F major is equally practical: A (3rd) open, D fret 3 = F (root), G fret 2 = A (3rd), C open (5th), F open (root). Five strings with only two fingers.

Open Sus4 Chords

Because every adjacent string pair is a perfect fourth, any two neighboring open strings give you a root-4th interval - the building block of a sus4 chord. Add one more open string and you have a complete sus4.

Standard Shapes in Fourths

If you already play guitar in standard tuning, you have a library of open chord shapes in your hands. Many of them transfer to P4 tuning with small adjustments. Here is the rule.

The bottom four strings (E-A-D-G) are identical in both tunings. Any shape that lives entirely on those strings works exactly the same. The top two strings are different: standard has B and high E, while P4 has C and F. That is one semitone higher on each string. So any fretted note on the old B or E string needs to drop by one fret. Any open note on those strings cannot translate - there is no fret below zero - so those strings get muted.

Below are the most common open chords. For each one, you will see the standard tuning shape, what happens if you play that same fretting in P4, and the corrected P4 version.

C Major

C major adapts cleanly. In standard, fret 1 on the B string gives you C. In P4 that same string is now C, so fret 0 (open) already gives you C - drop one fret. The high E string at fret 0 was giving you E (the 3rd), but fret 0 on the F string is F, not E. No way to lower it further, so mute it. The result is a solid four-note C major on the bottom five strings.

A Major and A Minor

The A shapes sit mostly on the middle strings. The only notes on strings 5 and 6 are the open high E (fret 0) and either fret 2 (A major) or fret 1 (A minor) on the B string. Drop those fretted notes by one fret and mute the open high E. Both chords come through clearly.

D Major and D Minor

D chords live on the top four strings in standard, which means two of those strings shift in P4. The adjustments are small - one fret lower on each of the top two strings. Both shapes feel natural and keep all four notes.

G Major

G major spans all six strings in standard. In P4, the open B string (fret 0) cannot translate, so string 5 gets muted. The high E at fret 3 drops to fret 2 on the F string, which gives you a high G - the root. You lose one string but keep five notes. Still a big, full chord.

E Major and E Minor

Here is where the trade-off shows up. E major and E minor both use open B and open high E strings - two notes that cannot drop below fret 0. So both top strings get muted. You end up with a four-string voicing on strings 1 through 4. It still sounds like E major or E minor, just thinner - more like a power chord with a third.

Translating standard shapes is a starting point, not the destination. P4 tuning has its own open chord vocabulary - the Am7, the open sus4 shapes, the open C and F voicings earlier in this lesson. Those shapes do not exist in standard tuning at all. The real payoff comes when you stop translating and start thinking in fourths.

Practice

Play through these open voicings slowly, letting each string ring. Try a progression using only open chords: C major, Am7, Dm, F major. Strum each chord twice at 60 BPM. Listen to how the open C and F strings tie everything together with a consistent tone across the changes.