What is double dropped d tuning?

Double dropped D tuning is a guitar tuning where both the sixth and first strings are tuned down one whole step to D. This tuning is also known as DADGBD tuning. It is mainly used in folk, blues, and rock music to create a fuller and richer sound, as it adds more depth to both the low and high ends of the guitar. Some popular songs that use double dropped D tuning include "Moby Dick" by Led Zeppelin, "She Talks to Angels" by The Black Crowes, and "John Barleycorn" by Traffic. It is also commonly used in slide guitar playing.