The word most harsh-sounding can have several antonyms, depending on the context in which it is used. Some possible antonyms include the words melodic, soothing, gentle, peaceful, and beautiful. Melodic suggests a pleasing arrangement of musical sounds, while soothing implies a calming effect on the listener. Gentle and peaceful both convey a sense of calmness and tranquility, while beautiful denotes an aesthetic appreciation. Depending on the context, other antonyms might be appropriate, such as pleasant, comforting, or mellow. Ultimately, the choice of antonym will depend on the speaker's intended meaning and the context in which the word most harsh-sounding is used.