Entrancing Melody

• WWizards of the Coast2017-09-29
  Official Ruling
  If a permanent has in its mana cost, X is considered to be 0.
• WWizards of the Coast2017-09-29
  Official Ruling
  In a multiplayer game, if a player leaves the game, all cards that player owns leave as well, and any effects that give the player control of permanents immediately end.
• WWizards of the Coast2017-09-29
  Official Ruling
  The control-change effect of Entrancing Melody lasts indefinitely. It doesn't wear off during the cleanup step.

Rulings via Scryfall