Antonyms for the word "under-tone" refer to loudness or volume. Some antonyms of "under-tone" include loud, boisterous, blaring, and strident. "Under-tone" means a low volume, so antonyms would indicate a higher volume. Therefore, antonyms include words like loud, noisy, and booming. "Under-tone" can also refer to something that is subtle or subdued, so antonyms may include words like obvious, blatant, or overt. In conclusion, antonyms for the word "under-tone" can refer to the opposite of its meaning in terms of volume or subtlety.