Sound film
The primary steps in the commercialization of sound cinema were taken in the mid- to late 1920s. At first, the sound films which included synchronized dialogue, known as "talking pictures", or "talkies", were exclusively shorts. The earliest feature-length movies with recorded sound included only music and effects. The first feature film originally presented as a talkie was "The Jazz Singer", released in October 1927. A major hit, it was made with Vitaphone, which was at the time the leading brand of sound-on-disc technology. Sound-on-film, however, would soon become the standard for talking pictures.
Sound film
A few innovative commercial directors immediately saw the ways in which sound could be employed as an integral part of cinematic storytelling, beyond the obvious function of recording speech. In "Blackmail", Hitchcock manipulated the reproduction of a character's monologue so the word "knife" would leap out from a blurry stream of sound, reflecting the subjective impression of the protagonist, who is desperate to conceal her involvement in a fatal stabbing. In his first film, the Paramount "Applause" (1929), Rouben Mamoulian created the illusion of acoustic depth by varying the volume of ambient sound in proportion to the distance of shots. At a certain point, Mamoulian wanted the audience to hear one character singing at the same time as another prays; according to the director, "They said we couldn't record the two things—the song and the prayer—on one mike and one channel. So I said to the sound man, 'Why not use two mikes and two channels and combine the two tracks in printing?'" Such methods would eventually become standard procedure in popular filmmaking.