Blackmail is Alfred Hitchcock's first talkie, and not a bad effort at all. The whole film was almost completed, when sound came in and revolutionized the industry; Hitchcock was forced to re-shoot some sequences and add others to make the film a mostly-talking film, something like Alan Crosland's The Jazz Singer (1927). Hitchcock's leading lady, Anny Ondra, had a very thick continental accent, not a problem for a silent film, but a real liability for a talkie. Hitchcock overcame the problem by having another actress speak the lines on-stage, offscreen, while Ondra simply mouthed them for the camera. Since dubbing was unknown at the time, this was the only method; then, too, the camera was confined to a soundproof shooting booth, and so the mobility of Hitchcock's camera is severely limited. During one long sequence, Cyril Ritchard as Crewe, the artist, sits down and plays a piano solo seemingly to keep the audience interested, but the film ends with a thrilling chase through the British Museum (mostly accomplished using miniatures, and the Schufftan Process, which allowed full-scale backgrounds to be reelected into the lens of the camera through a series of mirrors). It's interesting to see how Hitchcock deals with sound, when it was clearly thrust upon him at the last minute, and while not a front-rank Hitchcock, it is still a remarkable historical document of an artist finding his way through a medium that has suddenly been transformed by advancing technology.
by Wheeler Winston Dixon review