One little note on learning by ear: Sing Out! published a set of 35 tapes to go along with their 1200 song collection: Rise Up Singing. In most of the tapes, the singer is concentrating on hitting the notes, rather than expressing emotion. Zowie! It makes some beautiful songs into utter dreck!

Similarly, the midi tunes in the DT are emotionless (though I convert them into emotion-rich voices as I listen, don't you?)

I guess all I'm saying is that learning by ear isn't foolproof. Learning by listening to great interpretations of the songs -- that's an entirely different matter.