One thing that I have noticed is that there can be quite a deffinate line between two similar pieces of music, supposedly from the same genre; one you like and one you hate.

It's as if you can adjust and appreciate the music as it alters in a particular direction but there comes a point at which the brain rebels and says enough is enough.

For example I'm fond of late 19th century/early 20th century, French school, church organ music (one of many odd genres that I'm into). I like Vierrne and Daquin and some Messian, but some of his pieces are just noise whereas others are masterpieces of dischord.

I get the same thing with voices, and I'm not talking about clarity of diction.
A voice that is too pure has no character, but you can consider it purely as an instrument I suppose.
A voice that has some slight inconsistencies has interest and a personality.
A voice that has too many warbles, or huskiness etc, detracts from the song. I'm afraid that I cannot listen to Shirley Collins without beig too distracted from the song for this reason.