Boyzone led tributes to their "friend and brother" Stephen Gately, saying he was a "beautiful person in both body and spirit".
Stars of the music world, including Sir Elton John and Andrew Lloyd Webber, praised the 33-year-old singer, calling his "untimely death" in Majorca a "tragedy".
Ronan Keating, Keith Duffy, Mikey Graham and Shane Lynch said: "We are completely devastated by the loss of our friend and brother, Stephen. We have shared such wonderful times together over the years and were all looking forward to sharing many more."
They continued: "Stephen was a beautiful person in both body and spirit. He lit up our lives and those of the many friends he had all over the world. Our love and sympathy go out to Andrew and Stephen's family. We love you and will miss you forever 'Steo'."
Sir Elton said: "David (Furnish) and I are stunned by this tragedy. Stephen was the kindest, gentlest soul. We send our love and condolences to his partner Andy and to all his friends everywhere."
And musical impresario Andrew Lloyd Webber added that Gately was "enormously talented". "I very much enjoyed working with him on Joseph and the Technicolor Dreamcoat and the Boyzone hit No Matter What - my biggest selling single," he said. "His death is a great loss to the musical world."
Phillip Schofield, who also played Joseph in the West End production, wrote on Twitter: "My God. What terrible news to wake up to. Poor Stephen. My deepest condolences to his friends family and fans. He was a really lovely guy".
Westlife band members Kian Egan, Mark Feehily, Nicky Byrne and Shane Filan said Gately was "friendly, positive spirit and a passionate performer".
Boyzone manager Louis Walsh's spokeswoman said he was "very shocked and exceptionally upset" and he had pulled out of the X Factor live finals.
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Former Taoiseach Bertie Ahern, whose daughter Georgina is married to Nicky Byrne of boyband Westlife, told the BBC's Andrew Marr show: "It's just such a tragedy.Boyzone and Stephen, they've all been part of Irish life and far wider than that, the last 15 years, and so successful, so it's a huge, huge tragedy. It's so sad."
