"Play it, Sam," says a stunning Ingrid Berman, cajoling Dooley Wilson into singing "As Time Goes By" before a moody Humphrey Bogart storms over to find his ex-lover sitting in his nightclub.
Wilson's character Sam first played the song on the piano for Bogart's character Rick and Bergman's Ilsa when they fell in love in Paris as Nazi troops advanced on the French capital.
The salmon-colored instrument is the star of more than 30 items from the 1942 black and white movie offered for sale on November 24 by Bonhams auction house and Turner Classic Movies.
Also on sale are the doors of "Rick's Cafe Americain," Bogart's nightclub where Bergman asks Bogart to help her fugitive Czech resistance leader husband escape to America.
Other lots include passports and transit papers created for the film, a final draft screenplay, signed photographs of the cast and production memos.
All of the lots come from a private collector.
"Bonhams is thrilled to represent this remarkable 'Casablanca' collection, certainly one of the most significant film memorabilia collections still in private hands," said Catherine Williamson, director of Entertainment Memorabilia at Bonhams.
The auction house expects the piano to sell for seven figures. It last sold for $602,500 at auction in 2012, below Sotheby's then estimate of $800,000 to $1.2 million.
The sale also features a host of other collector pieces from other films, including a test dress and pinafore designed for Judy Garland for the 1939 production of "The Wizard of Oz."
The items will go on display in preview exhibitions held in Los Angeles from November 6-9 and in New York from November 20-24.
"Casablanca" is ranked one of the greatest American films of all time by the American Film Institute.
The Warner Bros movie won three Oscars in 1943 for Best Picture, Best Writing (Screenplay) and Best Director.
It is perhaps best known for Bogart's catchphrase to Bergman "Here's lookin' at you, kid."