Explain how early sound era directors René Clair and Ernst Lubitsch incorporated nonsynchronous sound into their films

What will be an ideal response?

The Frenchman René Clair believed that sound should be used selectively,
not indiscriminately. The ear, he believed, is just as selective as the eye, and sound
can be edited in the same way images can. Even dialogue sequences needn't be
totally synchronous, Clair believed. Conversation can act as a continuity device,
freeing the camera to explore contrasting information— a technique especially
favored by ironists like Hitchcock and Ernst Lubitsch. Clair made several musicals
illustrating his theories. In Le Million, for example, music and song often replace
dialogue. Language is juxtaposed ironically with nonsynchronous images. Many of
the scenes were photographed without sound and later dubbed when the montage
sequences were completed. The dubbing technique of Clair, though ahead of its time,
eventually became a major approach in sound film production.
Several American directors also experimented with sound in these early years.
Lubitsch used sound and image nonsynchronously to produce a number of witty and
often cynical juxtapositions. The celebrated "Beyond the Blue Horizon" sequence
from his musical Monte Carlo is a good example of his mastery of the new mixed
medium. While the spunky heroine (Jeanette MacDonald) sings cheerily of her
optimistic expectations, Lubitsch provides us with a display of technical bravura.
Shots of the speeding train that carries the heroine to her destiny are intercut with
close-ups of the whirring locomotive wheels in rhythmical syncopation with the
huffing and the chugging and the tooting of the train. Unable to resist a malicious
fillip, Lubitsch even has a chorus of suitably obsequious peasants chime in with the heroine in a triumphant reprise as the train plunges past their fields in the countryside.