Open C tuning brings the six open strings to sound a broad, deep C major chord. You'll see it written as C G C G C E, from the 6th string to the 1st. It's the lowest of the most common open tunings, because the 6th string drops a full two whole steps, from E to C.
In short: lower the 6th from E to C (two whole steps), the 5th from A to G, and the 4th from D to C, then raise the 2nd from B to C; the 3rd and 1st stay the same as in standard tuning. The result is C G C G C E, a deep C major.
What Open C tuning is
Open C is an open tuning: the six open strings already form a chord — in this case a C major — because they contain only the notes C, E, and G. Strum the open strings and you get a full C chord instantly, and sliding a barre up and down the neck changes the chord while staying major.
Its defining trait is depth: with the 6th string down at C2 (65.4 Hz), the low end opens up dramatically compared to standard tuning. It's a color loved in modern acoustic fingerstyle, often associated with songs like John Butler's Ocean. If you want to explore other, brighter open tunings, check out Open G and Open D.
How to get there from standard tuning
Start from standard EADGBE tuning and change four strings; two stay put:
- 6th string: from E2 to C2, down two whole steps. It's the string that changes the most.
- 5th string: from A2 to G2, down a whole step.
- 4th string: from D3 to C3, down a whole step.
- 2nd string: from B3 to C4, up a half step. It's the only string that goes up.
- 3rd string (G3) and 1st string (E4): stay unchanged.
Take it slow and double-check a couple of times: lowering three strings reduces the overall tension on the neck, and the other notes tend to drift down slightly. With a browser-based chromatic tuner like EasyGuitarTuner, you play each open string and bring it to the target note listed below.
String frequencies in Open C
| String | Note | Frequency |
|---|---|---|
| 6th | C2 | 65.4 Hz |
| 5th | G2 | 98.0 Hz |
| 4th | C3 | 130.8 Hz |
| 3rd | G3 | 196.0 Hz |
| 2nd | C4 | 261.6 Hz |
| 1st | E4 | 329.6 Hz |
Watch the tension on the 6th string
This is the most important thing to watch out for. Taking the 6th string from E down to C drops it two whole steps: the string loses a lot of tension and can end up floppy, with unstable intonation and a tone that tends to buzz against the frets.
The practical fix is to fit a set of slightly heavier strings, with a bigger gauge especially on the 6th, or a set designed for down-tunings. A thicker string holds decent tension even on very low notes, giving you a more defined attack and stable intonation. The same rule applies to other down-tunings like Drop D, where the 6th string also sits below its standard pitch.
When to use Open C
- Acoustic fingerstyle: the open strings ring together and build a rich harmonic bed even with just a few fingers. This is one of the tuning's natural homes — find more ideas among the fingerstyle tunings.
- Drones and pedal tones: the three Cs and two Gs, repeated across different octaves, act as a natural pedal point, perfect for modal, hypnotic songs.
- Slide: like every open tuning, Open C is well suited to slide guitar, because a straight barre always produces a major chord.
- Big, deep sound: the extended low end adds weight to intros and outros, even in a more modern, percussive style.
How to get back to standard tuning
Reverse the steps: raise the 6th from C back to E, the 5th from G to A, and the 4th from C to D, then lower the 2nd back from C to B. The 3rd and 1st are already in place. Recheck every string a second time, since putting the neck back under tension can nudge the notes you already set.