The phrase "discoursing about" is often used to mean speaking at length about a particular topic. However, if you're looking to mix up your vocabulary, there are many synonyms you can use. "Expounding upon" suggests a more detailed and thorough explanation, while "ruminating on" implies a more reflective or thoughtful approach. Alternatively, you could try "deliberating on" to indicate a more careful and considered discussion or "elaborating on" to suggest adding additional details or contextual information. Ultimately, the synonym you choose will depend on the specifics of what you're discussing - but by branching out from "discoursing about," you'll be able to convey your thoughts and ideas in fresh and interesting ways.