SonoBus:
It’s dead simple, free, P2P, and designed for remote music collaboration, so much lower latency than Discord. Even compression is optional and configurable, and it includes built in, tweakable filtering and gain settings.
And it works on everything. Android, iOS, desktop, all without any login. There’s a public server to start the initial connection (after which it’s purely P2P), but that’s self hostable if you wish.
It is a crime it’s so obscure. It’s basically perfect voice calling (and only voice calling), as long as everyone’s internet isn’t truly awful.