In a related vein, some mispronunciations of vowels are especially grating (to me, at least) when sung. An example is "The Star Spangled Banner." I've heard far too many really good singers sing "thru the pair-uh-liss fight..." (instead of "...pair-ih-luss...". That pronunciation would probably pass unnoticed in speech, but it stands out like a sore thumb when sung with sustained syllables as in that song.

Genie