The Yamaha piano was purchased in 1975 by Mercury, who died of AIDS in 1991 at age 45. The instrument could fetch a value of two to three million pounds ($2.5 million to $3.75 million) Some 1,469 lots will be auctioned at the London house, whose façade was decorated with a huge moustache. The collection was put up for sale by Mary Austin, a close friend who became Mercury's fiancée. Part of the proceeds will be donated to the Mercury Phoenix Trust and the Elton John AIDS Foundation, two organizations involved in the fight against AIDS.