[SOUND EDITING] IDEAS ON HOW TO DISGUISE A SONG'S VOCALS

I have a songwriting minigame in my game, in which the player can write the lyrics to a song.

After that, the song will be performed, and I'll use an actual music file.
Originally I was thinking of using an instrumental track and the lyrics would only appear written.
But now I want to use a track with vocals, but I'm trying to think of a way to disguise, or maybe "blur" the vocals a bit so they sound meaningless and it's easier for the player to "imagine" he's singing his own lyrics.

Ideas on how to do that?
I don't have the vocal/instrumental tracks separate.
The best idea I have so far is, since the performance will happen on a concert, use loud crowd wounds whenever the vocals appear, so they'll be almost indistinguishable. But I wonder if there are ways to do that with sound editing. I use Audacity.

That's actually a good idea. I'll see if I can get the instrumental samples of the part with vocals.

author=CashmereCat
If there's a lot of the track that's similar, you could sync the song with the BPM and take parts of the track that are instrumental and replace the vocals with them.

If you use this method, but still wanted to hear "blurred" vocals on top instead of just instrumental, you could layer the "original version" on top of the "edited instrumental" and use a low-pass filter (or hi-pass filter, maybe put some effects like reverb, etc) on the "original version" so that there's muffled vocals there.

Depends on the song, really. If I knew the song I'd be able to use more in-depth techniques, or even give it a go myself, if you're okay with that. You know where to find me ;)