The term 'mellifluent' refers to a pleasingly smooth and rich voice or tone. However, antonyms for this word would describe harsh, unpleasant, or grating sounds. Some examples of antonyms for 'more mellifluent' could be raucous, discordant, cacophonous, jarring, or shrill. These words suggest an unpleasant or irritating quality to sound, unlike the smooth and soothing tones of mellifluent speech. Using these antonyms can help to create a vivid contrast in writing or speech, emphasizing either the positive or negative qualities of a particular sound or voice.