The parades are very carefully choreographed and timed, with a lot of things working in harmony.
As for the music, there is a base track that plays along the route, using all the hidden speakers in the buildings and light poles. The intro spiel is played zone by zone, as the lead float approaches that zone. Then, it just loops the same harmony throughout the duration of the parade.
Then, each float has on-board speakers which play the float-specific melody. The floats loop their own music over and over as well. The float melodies sync perfectly with the underlying harmony played along the route using a wireless SNTP time synchronization system. For the sake of simplicity, SNTP uses an inaudible pulse that syncs multiple computers.
In the MK, they used to track the locations of each float using radio transmitters embedded in the pavement, but I believe they've abandoned that system and monitor the parade by way of multiple cameras, and human spotters. Via radio communication between Parade Control, the floats, and spotters, they keep the floats spaced appropriately. Drivers will speed up or slow down based on direction from Control and spotters.
The performers just repeat their routines over and over, and follow along with the tempo of the music. Certain floats with "speaking" characters will have some phrases that play on the on-board speakers. The furry characters know when they play, and will gesture accordingly (as if they're speaking).
As for getting ready, the time varies based on the role. Some performers can get ready in mere minutes, while others take much longer to get dressed, do hair and make-up, or don their fur.
I believe it takes around an hour to get all the floats out of the barn and line them up in starting position. They can't stage them too early, or the batteries will not last.
I'm sure there are former/current parade performers on here who can offer more specific information, but this is the gist of it.
