Musical stars paid emotional tributes to legendary US singer and actress Whitney Houston as they gathered for the annual Grammy Awards, less than 24 hours after her shock death, aged 48.

Organizers hastily added a performance by singer Jennifer Hudson to the awards show, as part of a "respectful" tribute at the Grammys, while the veteran producer who discovered her said Houston would want the show to go on.

"Simply put, Whitney would have wanted the music to go on," said Clive Davis, Houston's mentor who said he was "personally devastated" by her death, which came hours before his traditional pre-Grammys party in Beverly Hills.

Houston, whose hits included "I will Always Love You" but whose career went downhill as she battled with drugs, was found dead in her room at the Beverly Hilton, shortly before Saturday night's party.

Her family issued a statement Sunday, saying: "We are devastated by the loss of our beloved Whitney. This is an unimaginable tragedy and we will miss her terribly."

Musicians, many already in Los Angeles ahead of the Grammys, lined up to pay tribute to Houston, who sold over 170 million records and also starred in movies before descending into a very public battle with substance abuse.

Jermaine Jackson, whose brother Michael also died in shocking fashion in Los Angeles three years ago aged 50, said his thoughts went out to Houston's gospel singer mother Cissy.

"I can imagine what she's going through, because I..., we've been through (this) with my mother and its very tough to lose a child, and for you to outlive your child," he told CNN.

A member of Houston's entourage called 911 after the singer's body was found mid-afternoon Saturday in her fourth floor suite, and paramedics arrived within minutes, but were unable to revive her.

ABC news reported that Houston -- who had been due to attend the Saturday night party -- was found "lifeless," in her bathtub, but the cause of death was not immediately known.

"There were no obvious signs of criminal intent at this time, and it is being investigated by the Beverly Hills police department," said a police spokesman on Saturday.

The body remained where it was found through the evening, even as the pre-Grammys party went on four floors below. It was eventually taken to the morgue in the early hours.

An autopsy is expected Sunday or Monday, but the results could take some time because of the need for toxicology reports, the TMZ celebrity news website reported.

Grammys organizers the Recording Academy hastily drafted in Hudson -- who was presented with a Grammy by Houston in 2009 -- to perform at Sunday evening's show at the Staples Center in Los Angeles.

"It's going to be something respectful. It’s not going to be a full-blown tribute, that's too early and it's too fresh at this moment. It's going to be something respectful to Whitney’s memory," producer Ken Ehrlich told CNN.

British soul sensation Adele and iconic 1960s band the Beach Boys were due to make comeback performances at the Grammys. Paul McCartney, Coldplay and Bruce Springsteen and the E Street band were also due to take the stage.

But Houston's death will cast a pall over the show.

Condolences poured in on Twitter from shocked fans and from the famous, as sadness over the news spread through the entertainment world.

"Heartbroken and in tears over the shocking death of my friend ... She will never be forgotten as one of the greatest voices to ever grace the earth," wrote singer Mariah Carey, who teamed with Houston for duet "When You Believe."

With a ferociously powerful voice and a dazzling range, Houston achieved stardom as the "Queen of Pop." She also appeared in hit movies such as "The Bodyguard" and "Waiting to Exhale."

Mentored by Davis, the pop-soul singer had a string of 11 number one hits in the 1980s and 1990s including "How Will I Know," "Saving all My Love for You," and "I Will Always Love You." Houston won six Grammys.

However she suffered a major career setback after admitting drug use during her tumultuous 15-year marriage to singer Bobby Brown, and her health spiraled downward.

Brown reportedly broke down in tears onstage late Saturday after learning of his ex-wife's death -- the pair divorced in 2007 -- but he went on with his performance with the reunited New Edition as planned.

Houston will star in a posthumous movie she finished working on before her death, poignantly about a singing group dealing with the troubles caused by fame and drugs.

"Sparkle," due out in August, is a remake of a 1976 film loosely based on the story of the Supremes, following three sisters as they battle with difficulties that a singing career brings.