A couple attributed to Jascha Heifetz (from my faulty memory)-

After a recital an admirer said to Heifetz "Your Stradivarius never sounded so beautiful". Heifetz held the instrument up to his ear and said "Funny, I don't hear anything."

Another admirer said "I'd give anything to play like you" and he responded with the query "Would you give 16 hours a day for your entire life?"