Final answer:
The tambourine, featuring small metal pieces called zils, is considered the most important instrument in Motown for its role in adding rhythmic texture to the music.
Step-by-step explanation:
The instrument that has been called the "most important instrument in Motown" and features a number of small metal pieces called "zils" is the tambourine. The tambourine was a fundamental aspect of the Motown sound, often used to provide a rhythmic counterpoint to the melodies and harmonies of the Motown songs. In the context of Motown, the tambourine added texture and energy to the music, complementing other instruments and vocals.
Motown music is well-known for its unique and influential sound, defined by soulful vocals, strong basslines, and distinct tambourine beats. The tambourine, with its jingling zils, helped to accentuate the rhythm and readily becomes a memorable part of the overall song structure in many Motown classics.