5 of 18:
Mariah Carey, another iconic pop singer with a vocal range as impressive as Whitney Houston's, Tweeted this in response to her death on Feb. 11, 2012:
'Heartbroken and in tears over the shocking death of my friend, the incomparable Ms. Whitney Houston. My heartfelt condolences to Whitney's family and to all her millions of fans throughout the world. She will never be forgotten as one of the greatest voices to ever grace the earth.'
(Pictured: Mariah Carey appears in a photo posted on her Facebook page on May 8, 2010.)