This is the standard set of tones used to tune a guitar. Most guitarist only use this tuning.A popular tuning for Celtic music. DADGAD tuning was used by Jimmy Page in the songs "Black Mountain Side" and "Kashmir".The sixth string is tuned down to C, giving a rich low sound. The open strings form a C major chord. Pressing down on all strings at any fret will give a corresponding major chord.Drop D is the same as standard tuning, except the 6th string is tuned down to D. This allows for very quick barre chord changes, and contributes to many modern metal sounds.This is a great blues and slide tuning. The Rolling Stones use open G tuning for "Start Me Up" and "Honkey Tonk Woman".This is very popular with slide players. The open strings form a D major chord.