Hi Paul, I don't know how you recorded or mixed it, but your song's audio volume is 'maxed out' (near peak level) throughout.
The resultant audio heard is 'over saturated' & harsh (to my ears) losing whatever subtle 'dynamic expression' there was in the original track recordings.
If you still have the original tracks, it would be nice to hear the result again after a far better remix,
because I think your wife's a nice singer and you an equally impressive player. I've included a JPG image (displayed in SoundForge) of your song: