Euphoniousness refers to the quality of being pleasing to the ear. There are many synonyms that can be used instead of this word. Melodiousness is one such synonym, referring to something having a sweet or pleasant melody. Harmoniousness is another alternative, emphasizing the idea of being in harmony or accord. Musicality is also an excellent synonym, emphasizing the idea of being musically inclined. Sonorousness is a more technical synonym, used to describe sounds that are deep, rich, and resonant. Ultimately, any of these words can be used to replace euphoniousness, depending on the context and the desired level of formality.