Soundux VS Linux-SonivoxEas

I don't have any personal experience with any soundboard stuff, so you'll have to research that yourself. A quick web search led me to Soundux: https://github.com/Soundux/Soundux

instead, use Soundux, a completely free soundboard that is open source and on github.

https://github.com/Soundux/Soundux ?

I've used the Soundux program a few times in order to play sounds through discord calls with friends.

Soundux is the only method I found to make it work... barely.

My mistake, should have mentioned it's pretty early on in development. Try Soundux instead. If you've got your audio sorted by folders (ie, a Sound Effects folder, a Background Music folder, etc) you can set each one up as a separate tab and cue them by clicking or hotkey. To set volume, you'll have to right click, and there's no smooth crossfade option yet, but it's easy enough to set sounds to loop and control them at will.

Not a "real" solution, but you can use Soundux to mix the application sound with your microphone: https://github.com/Soundux/Soundux. Would still be great if Discord would fix the issue.

Ahh, I use Soundux which works insanely well.

The Linux-SonivoxEas project on Github I linked to has a downloadable release for use on Linux. If you have access to a Windows machine then there's this older eas-midi project that is derived from the same synthesiser source code that includes a Windows executable that can render a MIDI file to a PCM WAV.