Audiences initially stayed away, thinking that "Farewell My Lovely", its original title, was yet another Dick Powell musical. When the studio changed the title to "Murder My Sweet", box office receipts picked up considerably.
For Moose Malloy's first appearance, reflected in the window of Marlowe's office, Edward Dmytryk couldn't get Mike Mazurki to appear large enough because the window was too far from the camera. Instead, he had a plate of glass placed between the camera and Marlowe's desk, then reflected Mazurki's image in that. On screen, the plate glass is undetectable, making the large reflection seem to be farther from the camera.
For the scene in which Marlowe is drugged, Edward Dmytryk showed Dick Powell falling through a sea of faces. In this he borrowed a trick from -Saboteur (1942) by having the camera pull back from the actor to make it seem he was falling. He had the camera accelerate as it pulled back, as well, to intensify the horror.
In a 1946 Saturday Evening Post article, Dick Powell wrote that the film was the result of his ten-year effort to escape musicals. Powell said that when he asked Charles Koerner for a "solid tough guy" character to portray, Koerner offered him the role of Philip Marlowe.
RKO was on the verge of bankruptcy when it signed up aging matinée idol Dick Powell to make a series of musicals. Powell only signed under the proviso that he could play a straight dramatic role first, so he was cast as Philip Marlowe. Attached director Edward Dmytryk was initially horrified at this casting decision.
Lindsay Marriott's car (driven to the jewelry rendezvous by Marlowe) is an Isotta Franchini 8A Spinto variant. This expensive Italian make was typically sold as a chassis with the owner selecting a custom body by a selected coach builder. The car used here is highly unusual (a 4-place convertible, split windshield, the original right hand drive was retained and features parade doors). Although the year is unknown it is likely a 1932. It featured a straight 8-cylinder engine and 4-wheel brakes.
Star Dick Powell, who was desperate to change his screen image, lobbied hard unsuccessfully for the role of Walter Neff in "Double Indemnity," but Paramount went with contract player Fred MacMurray. His role in "Murder, My Sweet" accomplished his goal. Both films were authored by Raymond Chandler. (Double Indemnity was based on a James Cain story.)
The trivia item below may give away important plot points.
To protect Dick Powell in the final shoot out, when Marlowe dives for Grayle's gun only to have it go off right in front of his face, Edward Dmytryk used the plate glass trick from the film's beginning to reflect the gunshot at a safe distance from Powell. Since Miles Mander had held the gun in his right hand in all other shots for that scene, he had to hold it in his left hand to disguise the reflection.