There are several synonyms for the phrase "write a song around" which essentially means to create a musical composition with a particular theme or topic. Some possible alternatives include "compose a melody about," "craft a tune centered on," "fashion a song based on," or "construct a musical piece inspired by." Each of these options conveys the idea of building a musical work around a specific concept, idea, or message. Depending on the context and situation, different synonyms may be more appropriate for conveying the desired tone or style of the song in question. Ultimately, the goal is to find the right words to capture the creative process of writing a song from scratch.