Sound in cartoons was still a fairly new concept in 1929. The Adirondack News explained how it worked in this syndicated piece published February 9, 1929.
You’ll notice the absence of any mention of dialogue in this story. Either there wasn’t any or it was recording separately.
As the last Disney Oswald was released in April 1928 and the first Lantz Oswald appeared on screens in September 1929, this would have been the period when the Winkler studio on the West Coast were making the cartoons. The first synchronised Oswald was “Hen Fruit,” released on Feb. 4, 1929.
GHOSTLY BANDS PUT SOUNDS IN MOVIES
Snores and Snorts Linked to Pictures at Night
Hollywood, Calif.—It is middle of the night and the great studio sprawls like a town of fantastic shadows between the dry river bed, and the barren hills.
One supposes there is a night watchman somewhere on the lot, but apparently be does not see the dim figures slinking one by one toward a barnlike structure, each carrying something, and each disappearing through the same small door in the building.
Heading away from the studio, they might have been taken for burglars escaping with their loot, but under the circumstances it is more reasonable to guess they are conspirators of another sort.
The interior of the building is dimly lit, but by mingling casually with the crowd one can see very clearly what they carried in—two saxophones, a galvanised-iron washtub full of tin cans, a cornet, a tuba, a clothes wringer, three phonographs, a school bell, several cowbells, a band-operated alarm gong, three sites of electric bells, innumerable tin, brass and wooden whistles, many assorted pieces of wood and metal, half a dozen panes of window glass and a metal cylinder of compressed air.
Jolly Looking Conspirators.
Obviously these are not the paraphernalia of arsonists or dynamiters; and, besides, even in the dim light, the conspirators have a jolly look.
It begins to look more like preparations for an old-fashioned charivari. Before one can ask who was married, however, the head conspirator explains everything:
“Our job tonight,” says he, “is to synchronise Oswald the Rabbit.”
Oswald, one learns, is the pen-and-ink hero of an animated cartoon which, in keeping with the modern craze for screen sound, must be embellished with music and noise-effects.
Six musicians, skilled in leaping nimbly from tune to tune in harmony with the action on the screen, take their places under one microphone.
Another microphone bangs near the table where all the bells and whistles are spread. A large man in overalls sits near the tubful of tin cans with a wooden paddle in his hands, as if waiting for the cauldron to boil; the other conspirators stand here and there between the microphones, ready to make the right noises at the right times.
Rehearse at Showing.
They rehearse with the picture running on the screen in front of them. As the main title of the comedy appears on the screen the orchestra leaps into an overture, while the other sound-smiths stand tensely waiting for their cues.
When the opening scene discloses Oswald sleeping in his bed, the orchestra dodges quickly into a cradle song while a lad within whispering distance of a microphone snores rhythmically and another specialist imitates the squeaking of the bed by running sole leather through the clothes wringer.
After each rehearsal the recording engineer in the sound-mixing booth, who hears all this as it will sound to an audience, suggests improvements.
And again and again the mixed symphony of harmonies and discords is rehearsed; then, “This is the picture, boys,” and they go through it once more, with the sound-recording apparatus registering everything on celluloid.
Along about sunrise the sound-smiths call it a night and go home, tired and hungry, but with a little glow of pride at the thought that their artistry has made it possible for the world to bear as well as see Oswald the Rabbit.