Why Does My Attention Wander when I Listen to Brahms?
Why does my attention wander when I listen to a Brahms Symphony (or almost any piece of classical music)?
Partial answer: Consider just about anything that is highly stimulating in a continuous manner (no letup). E.g.
[a] The best steak you ever could imagine - sizzling, fragrant, oozing rich juices.
[b] NBA championship game, front row center court.
[c] Your loved one looks you in the eye and tells you for 15 minutes how wonderful you are.
In any of these examples, it would be natural for your attention to wander! In situations like this, sustained focused attention is just not doable for long periods.
The “problem” with a Brahms Symphony (or almost any longer piece of great classical music) is that the stimulation is sustained, without much letup. Sure, there are periods where the music is relatively “quiet”; but even then, there is plenty going on. Pick any passage from Brahms Fourth at random, and dwell on it, it is almost guaranteed to be a rich, satiating experience.
So the explanation for wandering-attention is: Too much sustained stimulation over a long period of time.