“sustaining rhythm that starts at 60 beats per minute and gradually slows to around 50”
A “rhythm”?? Really? I sure don’t detect any remotely close to 60 bpm.
Yeah, they screwed up the difference between tempo and rhythm. Rhythm is about the distance between major downbeats. Tempo is the speed of those downbeats. While I can't read music, I am a drummer. Also, 60 bpm IS slow. Think 60 seconds in a minute and 60 down beats is about one down beat per second. Try doing the count. One and two and...