And, this time, it isn't actually from me. Nor is it specifically a Brewers theme song. It is, in fact, by New Jersey experimental electro-acoustic musician/multi-instrumentalist, Doug Seidel, and it is a baseball theme, in general.
Here is a detailed, more helpful description than I would probably end up giving from the Soundcloud comments section, where Seidel, himself, explains to a curious listener his process used in 'Solo For Ball':
"This was rolling a baseball around in a stainless steel salad bowl, and holding a guitar pickup on the bottom. Wanted to use different periodic activity to make waveforms, etc."
Enjoy the sound of baseball! If you are wanting to listen to Seidel's quirky, thoughtful, complex, and often exciting sounds, they may be accessed here, on his page. Although he does not specifically do baseball-themed music, just about everyone enjoys some kind of music, so there's no reason to place these restrictions on anyone/anything. And, musically speaking, he has turned out to be a big influence on my approach, in the 2 or so years since I've met him. So, in a sense, the Brewers theme music in some way may have been influenced by the musician who, as it would turn out, thought to put a baseball in a salad bowl. Cheers, Doug!
(Note: The graphic above indicates "song", and probably should have indicated "music" or just them, instead. The baseball maybe thought it was a song, though).