In this talk, we will build a collaborative music composition environment from scratch using Elm and Elixir. We'll walk through the design of a collaborative music composition environment using Elm for a frontend that interacts with a Phoenix-channels based backend. We'll see how we can use the building blocks that Phoenix provides to allow us to build collaboration and persistence features to an Elm-based frontend and represent the frontend application's data structures and actions nicely in Elixir for persistence and transfer.