The phrase "amorous murmur" typically refers to soft, whispered words of affection shared between lovers. However, there are many synonyms that capture the same essence of intimacy and passion without using those exact words. For example, you might describe the "breathy whispers" of two people in love, or the "sweet nothings" that they exchange. Other options might include "hushed endearments," "romantic words," or even "passionate murmurs." Ultimately, the specific synonym that you choose will depend on the context of the sentence and the emotions that you want to convey. However, all of these phrases offer a sense of tenderness and desire that are central to the concept of the amorous murmur.