Possible Clues:

• Last part of some plays
• When ''eye of newt'' is mentioned in ''Macbeth''
• When "eye of newt" is mentioned in Macbeth
• Part of ''The Tempest''
• Last part of 'Aida,' e.g.
• When ''Ave Maria'' is heard in ''Otello''
• Last part of Aida
• "Double, double toil and trouble" time
• When Aida dies in Verdi's 'Aida'
• Play ender, often