This is going to be a wild stab in the dark but here goes.

I found a mge file of Your Mother Should Know by the Beatles. When I load the song it is asking for the following style

mothersh.sty

It is not one of the PG Music styles supplied with BIAB and I was unable to find any hint of it using a Google search after looking at 13 pages of listings.

Anyone heard if this style at all?

Bob Norton style?

Any info would be appreciated.

Not a really big deal, just wanted to hear what the song sounded like with the authors chosen style.

Sounds like you came upon an old file from the era when BBox users were making their own custom midi based styles left and right. In other words, very much a thing of the past.
So I'm afraid your only hope would then to either find someone who still uses such an old version of the app and just happens to have grabbed that song at the time - or an even longer shot, find the actual creator of that song! So I'm afraid this is gonna be worse of a hunt than that infamous haystack needle