A piano used in the classic Bogart and Bergman film Casablanca sold for just over $600,000 yesterday, falling far short of predictions that it could fetch $1 million or more.

The 58-key upright piano on which actor and singer Dooley Wilson performed "As Time Goes By," the signature song of the 1942 film's star-crossed lovers played by Humphrey Bogart and Ingrid Bergman, sold at Sotheby's for $602,500 (£372,600) including commission.

The auction house had assigned the iconic prop a pre-sale estimate of $800,000 to $1.2 million, given some astonishing prices attained by movie memorabilia in recent years.

In the film, the character Sam (Wilson) plays the signature song "As Time Goes By" during flashback scenes set in Paris, as well as in Bogart's club in Casablanca, where he and Bergman rekindle their romance.

Bergman's memorable lines included the imploring: "Play it, Sam. Play 'As Time Goes By.'"

Sotheby's had sold the piano, which was the one used during the Paris flashback scenes, to a Japanese collector in 1988, who paid $154,000 (£95,000), one of the highest prices ever paid for a movie prop at the time.

The film, set in Morocco during World War Two, won three Academy Awards including best picture, best writing and best director for Michael Curtiz.

The auction house did not identify the buyer.