Related Clues:

• Bit of planning
• Barbershop quartet part
• Carreras or Caruso
• Riccardo, in 'Un Ballo in Maschera'
• Headlight?
• Brain wave
• Flash of inspiration
• Edison product
• Voice range
• Matter for the gray matter
• Meaning
• Vocal range
• Head light?
• It's formed in your head
• Birth of a notion?