Open D Tuner Online — DADF#AD Slide Guitar

Open D tuning is DADF#AD from low to high, sounding a D major chord when the strings are played open. The sixth, fourth and first strings are the root D in three adjacent octaves. It is used for slide guitar, folk fingerpicking, and capo positions that raise it to open E.

How to use it

1. Start from standard tuning. The fifth and fourth strings stay exactly where they are, which gives you two stable anchors while you move the others.
2. Lower the sixth string from E2 to D2 (73.42 Hz).
3. Lower the third string from G3 to F#3 (185.00 Hz). This is a semitone drop, and it is the note that makes the chord major rather than suspended.
4. Lower the second string from B3 to A3 (220.00 Hz).
5. Lower the first string from E4 to D4 (293.66 Hz).
6. Strum the open strings. You should hear a D major chord. Check the fifth and fourth strings first if anything sounds wrong, because they should not have moved at all.
7. Add a capo at the second fret for open E. The shapes stay the same and every note rises a whole tone.

For a quick ear check without the display, play the open fourth string (D3) against the open sixth (D2) for an octave, then the open third (F#3) against the open second (A3) to hear the major third and fifth of the chord.

Open D string frequencies

String	Note	Frequency (A4 = 440 Hz)
6th	D2	73.42 Hz
5th	A2	110.00 Hz
4th	D3	146.83 Hz
3rd (major third)	F#3	185.00 Hz
2nd	A3	220.00 Hz
1st	D4	293.66 Hz

What open D does to the fretboard

Open D spreads the tonic across three strings, and that layout is what shapes the tuning:

• The root is on the sixth, fourth and first strings. D sits at the bottom of the tuning, in the middle of it and at the top, so a bass note under a melody picked on the first string is the same note two octaves apart. That spread is the drone effect the tuning is used for.
• F#3 is the major third, and it is the string that barely moved. The third string dropped only a semitone from G3, so it sits close to its standard position under your fingers. It is the note that makes the open chord unambiguously major.
• The fifth and fourth strings do not move at all. A2 and D3 stay at their standard pitches, which makes them the reference points for the whole tuning: the fourth string is the octave check for the dropped sixth, and the fifth is the fifth of the chord.
• Capo at the second fret and the tuning becomes open E. The shapes stay exactly the same and every string rises a whole tone. Players who want the key of E fit a capo rather than winding every string up.
• The moveable shapes sit at the fifth and seventh frets. With the open strings forming the I chord, IV and V are barre positions up the neck. Chords outside the key need shapes that have nothing to do with standard tuning.

The major third on the third string is the practical difference from DADGAD: open D always sounds major, while DADGAD has no third in the open strings and floats between major and minor until you fret one.

Accuracy and limits

• D and A each repeat across the tuning. D is on the sixth, fourth and first strings (D2, D3, D4) and A on the fifth and second (A2, A3). If a neighbouring string rings, the display can report the same note an octave away — the right note, the wrong string. Mute the others and check the card for the string you played.
• The fifth and fourth strings never move. They are the tuning’s anchors: if they read correctly before you start, they should read correctly at the end. A wrong reading there almost always means the microphone is hearing a different string rather than a drifted one.
• F#3 is spelled Gb3 by some other tuners. Same pitch, different name; the card keeps F# because that is the note’s job in a D major chord. It is also the string that moved only a semitone, so it sits closest to where it was in standard tuning.
• The dropped sixth string is the low note the microphone handles least well. D2 at 73.42 Hz is a whole tone below the E2 of standard tuning, and small laptop and phone microphones are least sensitive in that region (typically below ~100 Hz). Pluck it firmly over the 12th fret and let it settle; the fourth string’s D3 is a clean octave check by ear.
• A very light or decayed pluck reads worst. If the reading flickers or jumps an octave, re-pluck and let the note settle rather than waiting on a fading string.

Safety

• All four changed strings move downward. The sixth, third, second and first strings drop in pitch, so reaching open D removes tension from the neck rather than adding it.
• Returning to standard needs small steps. Raise the sixth, second and first strings a whole tone each, and the third string a semitone. Come up to the target from below and never force a peg that binds.
• Take care with the third string. It is a plain steel string under relatively high tension in standard tuning. Raising it from F#3 back to G3 is only a semitone, but a rushed turn can still break it.
• Do not detune to compensate for a capo. A capo at the second fret raises pitch, and that is the intended result. Slackening the strings underneath defeats the tuning.
• If the low D rattles, adjust the setup. Slide players often use heavier strings and higher action; tuning sharp is not a substitute for either.
• Let the neck settle. Four strings moving at once changes the load on the instrument. After the first pass, wait a moment and check all six strings again.