Do week old replies get read here? Anyway as I understand it a common songwriting process for Genesis was for the band to record an instrumental track and Gabriel then to come up with a vocal melody and lyrics and record those over the instrumental track (Banks or Rutherford or Collins or maybe all of them complain somewhere about Gabriel singing all over Battle of Epping Forest and not leaving any just-instrumental stuff). Not always though - in the case of "Dancing with the Moonlit" you can hear Gabriel working out the melody before he has words on Youtube: https://www.youtube.com/watch?v=POuwMAIk0b4 As for why that one's so good, love Gabriel like a sister but he had some help - one of the band members noted somewhere that he was into Elgar at the time, and it does sound to me a whole lot first theme (or something) of the first movement of Elgar's cello concerto: https://www.youtube.com/watch?v=OPhkZW_jwc0&t=2m47s (2 minutes 47 seconds)