Israeli Singers Richard Goodall Peter Marshall Hozier Christina Aguilera Reality Show Contestants Cover Artists Auditions Musicians Mireille Mathieu Tenors Adele Contestants Whitney Houston Ella Endlich Classical Singers Stevie Wonder Jeremy Beloate Jennifer Lynn Sofronio Vasquez Filipino Singers Filipino Artists Iranian Singers Loi Carrie Underwood Monali Thakur Rod Stewart Countertenors Marianne Rosenberg Heino Giovanni Zarrella Colette Mansard Sonu Nigam Roberta Flack American Idol Contestants Louane Coaches Johnny Mathis Duke Fakir Competition Kelly Clarkson