A rhythm instrument is any instrument used to create a musical rhythm. The four crossword solutions for the term 'rhythm instrument' are DRUM (4 letters), TUBA (4 letters), maraca (6 letters), and CASTANETS (9 letters). A DRUM is a percussion instrument consisting of a hollow shell or cylinder with a membrane stretched over one or both ends that is struck with sticks or hands. A TUBA is a large, conical-bore brass instrument that produces a deep, low-pitched sound. Maracas are a pair of small, hollow, gourd-shaped percussion instruments filled with seeds or beans that are shaken to produce a rattling sound. CASTANETS are a pair of small, hollow, wooden clappers held in the hand and clicked together to produce a sharp, clicking sound.