Possible Clues:

• American-born soprano, hailed as La Divina
• Opera emcee?
• Tony soprano?
• 20th-century Greek-American soprano
• Singer known as 'La Divina'
• Greek diva
• Mum's brought in song — summon singer
• Renata Tebaldi rival
• With uplifting impact, I excited La Scala
• Opera legend who was close to Onassis