I don't think you would have to "undo" an
"Echo" just shows in your Terminal whatever it is that you "echoed".
It does not do anything to your sound.
Just hit 'enter' and keep going - no harm, no foul.
echo "load-module module-detect" | sudo tee -a /etc/pulse/default.pa
this is the command I ran, I am just trying to figure out how to undo it. I tried "rev" but that did not do anything.
The reason I am asking is because this command made it to where there is no sound options at all and I don't know how to fix it without undoing it somehow.