Use the adjective mellifluous to describe something that sounds sweet and smooth, like the honeyed voice of a late-night radio DJ.
You might think that that mell in mellifluous has something to do with mellow. Actually, it's related to Melissa. In Greek mythology, Melissa was a nymph who discovered that you could eat the smooth, sweet stuff that bees make. Honeybees were named after her, and their tasty product was called meli. Mellifluous means to "flow as if with honey."