Mumble is VOIP (Voice Over Internet Protocol) software that allows people to communicate in real time. It's a popular privacy-respecting alternative to software such as discord, ventrilo, or teamspeak.
This server is hosted in addition to the Canchat.org XMPP server, and is completely public and free for anyone to use.
If you have mumble installed, you should be able to click the "Connect" button at the top of this page. If that does not work, here are some additional instructions.>