Open D Tuning for Guitar

Open D runs D2, A2, D3, F#3, A3, D4, in playing order. The lowest-pitched string is D2 (73.42 Hz) and the highest is D4 (293.66 Hz), measured against A4 = 440 Hz. Those are the exact target frequencies the tuner on this page listens for.

4 of the 6 strings move: E2 down 2 semitone(s) to D2; G3 down 1 semitone(s) to F#3; B3 down 2 semitone(s) to A3; E4 down 2 semitone(s) to D4. Work through them in order, then go back and re-check the first string — retuning shifts the neck tension slightly, so the earlier strings drift as you go.

Strummed open it sounds a D major chord, which makes a barre across any fret a full major chord — the reason slide players favour it. Five of the six strings are D or A, so the drone is heavy and the tuning suits modal, droning material more than fast chord changes.

D2 is 73.42 Hz at concert pitch (A4 = 440 Hz). That's the fundamental — the string also produces harmonics above it, which is why a tuner reading the wrong octave usually means it locked onto a harmonic rather than the fundamental. This is the lowest string in this guitar tuning.

The open strings spell D, A, D, F#, A, D — root, fifth, root, third, fifth, root. Because every string belongs to the chord, a straight barre anywhere produces a complete major triad, which is the property slide playing depends on entirely. The cost is that the tuning is committed: the third sits on the third string, so reaching minor requires flattening that one string rather than adjusting a fingering. Five of six strings being D or A also means the tuning drones heavily, favouring modal and vamp-based writing over music that needs to move between distant keys.