A chromatic tuner is a device used by musicians to accurately tune their instruments. It detects the pitch of a sound and displays whether it is in tune, sharp, or flat. This helps musicians ensure that their instruments are properly tuned to the correct notes. Chromatic tuners can be found in various forms, including handheld devices, smartphone apps, and built-in features on some instruments. They are useful for tuning a wide range of instruments, such as guitars, violins, and pianos, making them essential tools for both beginners and experienced musicians.