The cello is a string instrument that belongs to the violin family. It is larger than a violin and viola but smaller than a double bass. The cello has four strings tuned in perfect fifths, typically to the notes C, G, D, and A. It is played while seated, with the instrument resting between the player's knees. Cellos are known for their rich, deep sound and are commonly used in various music genres, including classical, jazz, and contemporary music. They can be played solo or as part of an ensemble, such as a string quartet or orchestra.