Final answer:
The organ is the keyboard instrument that uses various sets of pipes to create contrasting colors. The air expanding in the pipes produces different resonant frequencies resulting in unique tones. Each pipe in an organ produces a particular tone based on its length and shape.
Step-by-step explanation:
The keyboard instrument that uses various sets of pipes to create contrasting colors is b. the organ. This is because an organ operates using air flowing through different lengths and shapes of pipes, each set carefully designed to produce unique and contrasting colors of sound. The organ can be modeled like a system of pipes with varying boundary conditions, either open at both ends or closed at either end.
Through a complex mechanism, when keys are pressed on an organ's keyboard, valves corresponding to certain pipes are opened. The air is allowed to expand in these pipes, and resonant frequencies are produced as longitudinal waves travel down the tubes, interfacing with reflected waves traveling in the opposite direction. In an organ, each pipe produces a unique tone based on its specific length and shape, hence creating a broad spectrum of musical colors.
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