"Drop D" is a guitar tuning where the lowest string, the sixth string, is tuned down one whole step from E to D. This adjustment allows for a deeper, heavier sound and makes it easier to play power chords, as they can be played with a single finger across the lower strings. This tuning is popular in various music genres, especially in rock, metal, and grunge. Many famous songs utilize drop D tuning, providing a unique tonal quality that enhances the overall sound. Musicians often appreciate its simplicity and versatility for songwriting and performance.