Here are links to the clips we used, with some notes.
1. https://www.youtube.com/watch?v=Qqe0GdUpJHs Vivaldi, Winter, Four Seasons (Allegro), with animated score
Four voices, each played by multiple instruments. Different speeds in the voices. Not all voices play all the time.
2. https://www.youtube.com/watch?v=RhKYJclQj5s Debussy, First Arabesque (piano solo)
3. http://www.yourepeat.com/watch/?v=hVb5orKdDDg&start_at=0&end_at=236 Debussy, First Arabesque (piano solo)
2 and 3 are the same music, notated differently. In 3. there are two streams, one for each hand (physical streams), but 2. has three logical streams.
Of course in all the above, we could claim there is just one stream, with multiple voices (a vertical slice at each time instant). This may well be appropriate for some kinds of tightly harmonized music, like barbershop.
4. https://www.youtube.com/watch?v=IHIQ838103U Bach, Cello Suite No. 1, 1st mvt. (showing bowing)
What appears to be one process from a distance may well consist of multiple processes working together. Here we see that playing a cello involves two hands, but the listener only hears a stream of single notes.
Music is parallel, indeed "real time".
But cinema has only one screen, and so the different stories have to be "context switched" onto the screen. Though unlike computing processes, they often run off-screen - we just aren't looking at them. The first example below also has the soundtrack from the baptism playing over all the stories, so they are tied together strongly temporally.
The second example uses synchronisation between stories by a telephone call, and by visual juxtaposition between the trains. The trains are linked to the other stories by intercutting and by references in the dialogue.
5. https://www.youtube.com/watch?v=BHVN24peVyQ Intercutting (Coppola, from the "Godfather"): we saw only two minutes at the start.
6. http://onlinemovies.pro/unstoppable-2010/ We saw a couple of minutes after 21:50.