What are the tiny pauses in the song Moonlight Sonata (1st mov)? Why does it sound like the beat is irregular yet it’s still pleasing to hear?

Question

First of all, this is an example of what I’m talking about: https://youtu.be/sbTVZMJ9Z2I

In that song, at least to my ears, there are very tiny pauses in the song. It feels like the tempo isn’t linear, it stretches a bit in places.

1. Are my ears playing tricks on me, or are they real?
2. If they’re real, why aren’t they in all renditions of the song? I notice some don’t have those pauses (and some stretch the beat slightly in other places?)
3. If they’re not real, what is happening with my ears?
4. What’s special about this song that it has such irregular beats? Why is it not used more in music? (regardless of whether it’s real or a ‘trick’)

Please tell me everything there is to know about this phenomenon (or what it’s called at least so I can look it up) because I’m obsessed with it. Thanks!

In: 73

Answer 1

So, I’ve heard both piano music linked here and I have absolutely no idea what y’all are talking about. Since this is ELI5, anyone has a video comparing “regular beat” with rubato?