Final answer:
The tambourine is the most important instrument in Motown music and features small metal pieces called zils.
Step-by-step explanation:
The instrument that has been called the "most important instrument in Motown" and features small metal pieces called zils is the tambourine. The tambourine is a percussion instrument that consists of a round frame with jingles (zils) attached to it. It is often played by shaking or striking the instrument with the hand or a drumstick.