How did Ernst Lubitsch keep the camera moving in early sound films?

In the early years of sound film, most directors were forced to keep their cameras stationary inside soundproof booths—often called "iceboxes"—to prevent the microphones from picking up the noisy whir of the camera motor.1

Ernst Lubitsch bypassed these technical limitations by utilizing postsynchronization (or dubbing). By filming sequences without dialogue and adding the sound later, he was able to free the camera from the restrictive soundproof booths and static positions that constrained other filmmakers of the era. This technique allowed him to maintain dynamic camera movement in his early sound musicals, such as The Love Parade (1929) and Monte Carlo (1930).23