Drop D: take your low E string and tune it down two half-steps to a D. The other five strings stay where they are. Now the lowest note on your guitar is a D, and any D-based chord rings huge.
How to drop D
Pluck your low E. Compare it to the open D string (4th string). Loosen the low E until it sounds an octave below the D string. Use the tuner to confirm: the note should read D2.
Open the chromatic tuner
Tunes by ear via your laptop or phone mic. Pluck a string, watch the indicator center.
Why it's worth it
In drop D, the D major chord shape uses all six strings (instead of just the top four). A massive, deep, ringing D.
D | open D string
D | open D string (4th)
F# | 2nd fret G string
D | 3rd fret B string
F# | 2nd fret high E (or open A)
D | open low (re-tuned) D
Strum all six. Now strum a regular D chord (top four strings only) in standard tuning. Hear the difference? Drop D adds power.
Movable power chords with one finger
In drop D, the bottom three strings are all a fourth apart, which means a power chord becomes a single-finger barre across the lowest three strings.
A D5: barre the open D-A-D strings.
An E5: barre the 2nd fret of the lowest three strings.
A G5: barre the 5th fret.
An A5: barre the 7th fret.
One finger, one barre, instant power chord. Soundgarden, Foo Fighters, every modern rock band uses this voicing.
Songs in drop D
Everlong (Foo Fighters), Heart-Shaped Box (Nirvana), Dear Prudence (Beatles, in this tuning), Holiday (Green Day, on the bridge).
90 BPM. Strum D5, then move that one-finger barre up to G5 (5th fret), down to E5 (2nd fret), back to D5 (open). Loop. Hear how rich the low end is.
Tuning back up
When you're done, retune the low E up to E. Tune up to pitch, never down (pegs hold up-tuning better).
Next: advanced Travis picking with hammer-ons.