Gonna leave this here in case it's useful to someone.

I once tried replacing some sounds with other sound effects replacing the wav files, but in-game it sounded like a horrible distorted mess.
Found out you can use audacity (or some similar audio editing software), and export the sound you want as "Other uncompressed files -> WAV -> Unsigned 8-bit PCM", then it sounds just fine in-game.

nice thanks - i was trying to lower the volume of click.wav
think we should drop it in the next release

If this works then it could open up the world of sound again.
I wanted to add a little tinkle bell for when your spells were running out but it sounded awful.

I have tried this method and successfully changed some sound effects around.

For example;

https://www.youtube.com/watch?v=ghoZbRpwUkU