A mouth organ, also known as a harmonica, is a small musical instrument played by using the mouth to direct air into or out of holes along a mouthpiece. Each hole contains a reed that vibrates to produce sound when air passes over it. Mouth organs are popular in various music genres, including blues, folk, and rock. Mouth organs come in different types, such as diatonic, chromatic, and tremolo, each offering unique sounds and playing techniques. They are portable and easy to learn, making them accessible for beginners and experienced musicians alike. The instrument has a rich history and is often associated with artists like Bob Dylan and Little Walter.