He does do it all himself, according to this profile that ran on CNN last year. And notice (at 04:25) that his lyric writing has drawn the admiration of Sondheim himself.
In addition to the qualities you mentioned, I watch his videos a second time to listen to his singing. He's really very, very good, and he seems to throw in a couple of subtle vocal embellishments that show off his capabilities in every parody. |
