The episode's finale, when all have "found their song":
At 1:21...WOAH, Jerry's voice really does record well.
This and "Let Me Be Your Song" (or whatever its actual title is) are probably my two favorite musical numbers from the show's entire run, really.
The most honest thing I can do is gush about this stuff. Have I attained this level of fervour? ;) (Thanks, GeoX!)