What adjective describes a sound that is rich and smoothly flowing?

The adjective that describes a sound as rich and smoothly flowing is "mellifluous." This term originates from the Latin word "mellifluus," which literally translates to "honeyed," evoking the idea of a sound that is sweet and pleasant to hear. When used to describe music, speech, or other auditory experiences, "mellifluous" suggests a soothing quality that is both harmonious and appealing, often evoking imagery of flowing, gentle sweetness akin to honey.

In contrast, the other options do not convey this specific auditory quality. "Macerate" refers to the process of softening something by soaking it in a liquid, which is unrelated to sound. "Lubricious" is an adjective that can mean oily or slippery, often used in a more figurative sense to describe behavior that is morally questionable or lascivious; it does not pertain to the quality of sound. "Officious" describes someone who is overly eager to offer help or advice, often in an intrusive manner, and likewise has no connection to the auditory characteristics of being smooth and rich.