ZDoom

Perhaps because Goldwave isn't supposed to be free? Besides, even such a 'simple' effect can be a daunting task for someone with little to no sound editing experience (though I can't speak for Gez on that part).

Still, there's always Audacity, if push comes to shove.

And if you try to purchase Goldwave, the appropriate page on their site says:

"Before purchasing a license, please download and install the evaluation version of GoldWave or MULTIQUENCE. You are welcome to evaluate the program over several days to ensure it performs the tasks you require."

Ergo, they WANT you to try before you buy.

With that in mind, I have to repeat the recommendation: for good audio editing software, download Goldwave.

I must've forgotten about that. Guess I am getting old.

For the record, I also use it myself and love it to death.

I know it's a bit of a bump, but I just put out a rip of Blood 2: The Chosen a few days ago that has some sounds that may be of interest for this particular project. The Zealot enemy also spoke in cultist language, but it was rather reserved in its tone in comparison to the original cultist sounds. Check out the thread and see if that doesn't fit your purposes a little better.