C tuning is a type of guitar tuning. The strings of the guitar are tuned two whole steps lower than standard tuning. The resulting notes can be described most commonly as C-F-A♯-D♯-G-C or C-F-B♭-E♭-G-C.
The tuning is commonly used by metal and hard rock artists to achieve a heavier, deeper sound. It also makes bending easier for the player than in E standard using the same gauge of strings. Heavier gauge strings can be used in order to maintain tension in the strings. It is possible to play without them, but difficulties can be experienced as it becomes quite easy to unintentionally bend notes and chords out of tune. However, the ease of bends can be desirable, depending on playing style of the musician.