Maybe you’re confusing acoustic with instrumental? For acoustic and instrumental are two different forms. Instrumental music is music without any lyrics/singing/rapping and therefor doesn’t necesarrily need a vocalist/singer. But, acoustic music is simply music without electrical amplification.
There have been made plenty of acoustic recordings in the past with marvelous singers. And like I mentioned in an earlier reply; Mike and Chester have already made a beautiful acoustic version to Final Masquarade. It is not impossible.
@samuel_the_leader
I’ve never seen that video version of What I’ve Done either btw. Very sci-fi, I like it.