Spoilers are precisely defined here. Rules vary by the story's medium. Info from television stories can't be added here until after the top or bottom of the hour, British time, closest to the end credits roll on BBC One. Therefore, fans in the Americas who are sensitive to spoilers should avoid Tardis on Sundays until they've seen the episode.
The Matrix Data Bank includes a listing of the nineteen televised occasions of the Doctor singing.
This issue's Archive Feature is the first with an extended Factfile in which Andrew Pixley explores the production and broadcasting of the story in more depth.
Additional Input from DWM 162: Mistakenly being related to DWM Issue 162! Episode Guide: 7B ran for four parts, not three. 7C, Parts Nine to Twelve is four not two. For Thirteen, Robert Holmes is script writer, Pip and Jane Baker Part Fourteen. Eric Saward was script editor on Part Thirteen Only. In the Archive Feature The Masque of Mandragora: Part Four achieved 23rd position in the Top Hundred with 10.6m viewers.
Additional Input from DWM 165: In the Episode Guide the number of episodes was wrong; Part Nine to Twelve is obviously three parts, not two, and the quote used to head Into the Vortex (the random quote from the contents page) did come from The Masque of Mandragora.