You don’t need vocal talent, but you DO need enthusiasm.
You need to warm up enough to lip-sync, or ideally sing along to some of these tunes.
As the nights move along, the band and DJ will also play “normal music”. It’s 100% guaranteed that you will know songs and end up singing (or shouting) from the top of your lungs.
Ps. it always ends the same way: standing on the benches, arms around strangers, full volume singing.
And that is what Oktoberfest is.