Dylan changes the way he does the songs all the time. For those who go to many of his concerts part of the enjoyment is seeing how differently he will do the song from the last time you heard it.

In terms of singing, he was doing some marvelous singing in the 60s, 70s, and 80s...was a bit unpredictable in the 90s (sometimes great, sometimes not so great)...but there has been a striking deterioration in his vocal powers in the last decade, I'd say.