I Want You (She's So Heavy)
Although the drop D tuning was introduced and developed by blues and classical guitarists, it is well known from its usage in contemporary heavy metal and hard rock bands. Early hard rock songs tuned in drop D include The Beatles' "I Want You (She's So Heavy)" and Led Zeppelin's "Moby Dick", both first released in 1969. Tuning the lowest string one tone down, from E to D allowed these musicians to acquire a heavier and darker sound than in standard tuning. Without needing to tune all strings (Standard D tuning), they could tune just one, in order to lower the key. Drop D is also a convenient tuning, because it expands the scale of an instrument by two semitones: D and D.