Open C tuning notes and frequencies
| String | Note | Frequency |
|---|---|---|
| 6 | C2 | 65.41 Hz |
| 5 | G2 | 98.00 Hz |
| 4 | C3 | 130.81 Hz |
| 3 | G3 | 196.00 Hz |
| 2 | C4 | 261.63 Hz |
| 1 | E4 | 329.63 Hz |
Sound and genres
Open C has the widest range of the common open tunings: string 6 drops four semitones to C2, while string 2 rises a semitone to C4. The bottom four strings are only roots and fifths (C G C G), so they work like a pianist's left hand, and the only third is the E on string 1.
So much fifth and octave gives open C a huge, resonant sound on an acoustic. Mute string 1 and the open strings become a C5 drone; fret string 2 at fret 3 for E♭ and the chord turns minor over the same bass.
- Fingerstyle
- Folk
- Ambient
- Singer-songwriter
- Slide guitar
How to tune to Open C
- Open C moves four strings, so take it one string at a time from standard.
- Lower string 6 four semitones, from E2 to C2. Turn Detect String off and tap the string 6 peg so the tuner stays on that string through the long drop.
- Lower string 5 two semitones, from A2 to G2, and string 4 two semitones, from D3 to C3.
- Leave string 3 on G3 and string 1 on E4. Raise string 2 one semitone, from B3 to C4.
- Check by ear: strings 6, 4 and 2 are C in three octaves, and strings 5 and 3 are G an octave apart.
- Run the final recheck pass in the tune-up checklist. With three strings slackened and one tightened, the first strings you tuned will have shifted.
Changing from standard tuning
String by string, from standard tuning. Pick a different starting tuning to see its changes, or open the tuning changer.
4 strings change
| String | Change | Semitones | Peg | Tension |
|---|---|---|---|---|
| 6 | E2 → C2 | −4 | ↓ Loosen | −37% |
| 5 | A2 → G2 | −2 | ↓ Loosen | −21% |
| 4 | D3 → C3 | −2 | ↓ Loosen | −21% |
| 3 | G3 | 0 | No change | — |
| 2 | B3 → C4 | +1 | ↑ Tighten | +12% |
| 1 | E4 | 0 | No change | — |
String gauges and setup for open C
A low C on a standard set is very slack, especially on an acoustic with light strings: it buzzes, flaps against the frets and goes sharp when you pluck hard. A heavier string 6, or a medium set on acoustic, keeps it firm. Buying a single heavier low string and keeping the rest of your set is a cheap way to try it.
If you keep a guitar in open C, check neck relief after a day or two. The overall pull on the neck drops, and a small truss rod adjustment may cure any new buzzing.
Chords and slide in open C
A barre or slide at fret 5 gives F, fret 7 gives G and fret 12 gives C an octave up, so the I, IV and V chords in C sit at the open strings, fret 5 and fret 7.
Small additions change the color without losing the drone: fret string 4 at fret 4 for Cmaj7, or string 1 at fret 1 for Csus4. Fingerstyle players often pick melodies on strings 1 to 3 over an alternating bass on strings 6 and 4, which needs no fretting at all in C.
Chord shapes in Open C
Songs in Open C
- Poor Tom — Led Zeppelin (1982)Source: Guitar World, 2025
- Question — The Moody Blues (1970). Justin Hayward's 12-string acoustic partSource: Guitar World, 2025
- Come to Me — Goo Goo Dolls (2013)Source: Guitar World, 2024
- As It Was — Hozier (2019)Source: Guitar World, 2024
- King of Spain — The Tallest Man on Earth (2010), capo 8Source: Fender
Frequently asked questions
What is open C tuning?
C G C G C E, low to high. The open strings form a C major chord with a low C bass.
Do I need heavier strings for open C?
On acoustic, medium strings or a heavier string 6 help the low C stay firm. On electric, a set with a heavier low end works best.
Is open C bad for my guitar?
No. Three strings are lowered and only string 2 is raised, by one semitone, so overall tension goes down.
What is the difference between open C and C standard?
Open C (C G C G C E) strums a C major chord and suits slide and fingerstyle drones. C standard (C F B♭ E♭ G C) keeps standard intervals four semitones lower, so normal chord shapes work.
How do I play minor chords in open C?
Mute string 1 and fret string 2 at fret 3 to put E♭ in the chord, which gives C minor over the open low strings.
Why does my low C go out of tune when I play?
A slack string goes sharp for a moment when plucked hard, so it sounds unstable. Pluck lighter, use a heavier string 6, and tune with the same touch you use when playing.