Drop D is the most common alternative guitar tuning because it changes only one string. Starting from standard EADGBE, you lower the sixth string a whole step from E to D, leaving the other five strings untouched. The immediate benefit is a lower, heavier bottom note that many rock and metal players rely on for riffs. It also simplifies power chords: on the lowest three strings, a barre across a single fret now sounds a full root-fifth-octave chord, so fast chord changes and palm-muted rhythms become much easier. Folk and fingerstyle guitarists use Drop D too, often to reach a low D drone that supports songs in the keys of D major or D minor. Because only the sixth string moves, returning to standard tuning is quick, which makes Drop D easy to try mid-set. A tuner that offers a dedicated Drop D preset, like FretMind, makes retuning that single string accurate and fast.