A tuner is a device used to measure and adjust the pitch of musical instruments. It helps musicians ensure that their instruments, such as guitars, pianos, or violins, are in tune with each other or with a specific reference pitch. Tuners can be electronic, using microphones to detect sound, or mechanical, like tuning forks. There are different types of tuners, including clip-on tuners, pedal tuners, and smartphone apps. Each type offers varying features, such as visual displays or sound feedback, making it easier for musicians to achieve accurate tuning. Proper tuning is essential for harmonious music performance.