A peer-to-peer sound mixing board that runs (almost*) entirely in the browser. Intended usage is for online tabletop (e.g. D&D and Pathfinder) sessions in which the DM wants to create soundscapes for their players. This can be downloaded and run as-is (although join links will not work; joining will have to be done via ID). Alternatively, you can use the hosted version here.
* A server is used to broker connections between users. By default, this uses the PeerJS official PeerServer
One user hosts a session, and other users can connect. Once connected, the host can add sounds (e.g. from a YouTube video link), and the connected users will hear the sounds as well. Multiple sounds can be added with their own volume controls.
In order of priority: