Despite Whitney Houston's death just hours before her mentor Clive Davis' annual pre-Grammy celebration -- in the very same hotel where the singer's body was found -- the party went on as planned.

Celebs came out for what was supposed to be one of the best parties of the year, but the evening turned into a memorial for host Davis' most successful recording act ever -- Whitney Houston.

Britney Spears and Kim Kardashian were on hand, along with Alicia Keys, Tom Hanks, Jennifer Hudson, Diana Ross, Brandy, Mary J. Blige and others, to remember the life of the 48-year-old superstar.

Davis led a moment of silence a the beginning of the evening and a source inside the party tells us: "The mood was somber. No one was 'celebrating' -- the evening became a tribute to Whitney Houston. Guests were hugging and crying."