Jul 15, 2008, 9:50 GMT
Whitney Houston's voice was almost destroyed by drugs.
Whitney Houston performs at the closing concert of the 'Mawazine' world music festival in Rabat, Morocco, 24 May 2008. EPA/ZACARIAS GARCIA
Following years of heavy smoking and drug abuse, Whitney's singing was reportedly "unrecognisable" when she began recording her new album.
A source told Britain's Daily Mirror newspaper: "She was smoking a lot and taking a lot of drugs. Her voice was almost unrecognisable."
Whitney - once dubbed 'The Voice' for her five octave range - was sent for singing lessons by industry executive Clive Davis and is now back to her high-note best.
The source added: "Thousands have been shelled out to train her back up to the original. But now she sounds terrific - she is going to blow everybody away."
Whitney's new, as yet untitled comeback album, is set for a November release.
In 2006, Tina Brown - the sister of Whitney's now ex-husband Bobby Brown - claimed Whitney was living in squalor, and hopelessly addicted to crack cocaine.
She released photographs to a US magazine showing the star's bathroom littered with drug paraphernalia, including a crack pipe.
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