Open Tunings and the Capo

An open tuning means the six open strings themselves combine into a complete major triad. The biggest convenience: whatever fret you barre with one finger, that's a same-named major triad raised by that many semitones — which is also the principle behind how slide blues can move through whole sections of harmony so easily.

Three common ones: Open D (D-A-D-F#-A-D, open strings = D major, deep and solid); Open G (D-G-D-G-B-D, open strings = G major, bright, common in folk and slide); Open C (C-G-C-G-C-E, open strings = C major, extremely thick, orchestral resonance, with the 6th string lowered two whole steps down to a very low C).

Lowering strings (most open tunings lower them) makes the tension looser and the touch softer; lower too far and the string goes floppy and rattles — for long-term use of a given low tuning, fit correspondingly heavier strings. Raising strings (like Open E) increases tension, with a risk of broken strings and stress on the neck, so it's not recommended for beginners to leave it tuned that way; if you want that sound, “a slightly lower tuning + a capo” is safer.

Clamping a capo on a fret = raising the whole guitar, one semitone higher per fret (the actual key = the key your hand is playing + the number of frets the capo is on). Three uses in fingerstyle: ① transpose the whole thing, to fit an ensemble or change the tone color; ② in a solo, clamp it on the 1st–4th fret (the 2nd is most common) for a brighter position; ③ pair it with an open tuning — for example Open D with the capo on the 2nd fret safely gives you the open resonance of E major, better than the tension-risky Open E directly.

An advanced trick: clamp only some of the strings and leave the rest open, and the effect is like “a changed tuning,” yet the strings are physically still in standard tuning — pop it off any time and you're back to standard, no drifting. The most classic use is to clamp a partial capo on the 2nd fret of the 3rd/4th/5th strings, which is like fretting an Esus4 for you, instantly giving an open sound close to “DADGAD a whole step higher,” while your left hand uses standard shapes as usual on the strings that aren't clamped.