Related Clues:

• Triad
• Musical group
• Beethoven's "Archduke," e.g.
• Three
• Rock's Green Day, e.g.
• Kingston --
• The witches in 'Macbeth,' e.g.
• Wooden shoe sailors, e.g.
• Andrews Sisters, e.g.
• Rock's Green Day, for one
• The Indigo Girls, e.g.
• Small musical ensemble
• Half a quartet
• 'Pop, culture, TV' network
• Comic skaters Frick and Frack, e.g.