Got a few questions actually. Firstly, is there a way for the music from the base game (Succession Wars) and the exclusives from the expansion (Price of Loyalty) to both be played in-game?

Secondly, apparently there was a HoMM II Gold release that included music from HoMM III (huh?). Is this the same with the GoG version?

Thirdly, what's all this about the tracks in the GoG release being low quality? I read that it's possible to fix for HoMM 1, but what about this one?

And while I'm at it, where's that Windows 95 version that people have been asking for since 2009? Everywhere I look in the forums, there's always something that tells me that what I bought isn't the definitive version. So many overwhelming details, so confused...

Simultaneously not. But if you have got the original CD releases of the game released by New World Computing/3DO (The Succession Wars - Nov 4, 1996, The Price of Loyalty - May 5, 1997) then you can swap the CDs (or CD images) and thus use different sound tracks ingame. I repeat again. There are three different variants of the HoMM II Soundtrack.
1. Heroes of Might and Magic II: The Succession Wars (original November 4, 1996 release).
2. Heroes of Might and Magic II: The Price of Loyalty Expansion Pack (released May 5, 1997).
3. Heroes of Might and Magic Millenium Edition disk 2 with Heroes II Gold re-release (August 26, 1999). This disk contains some CD-quality audio tracks from HoMM III.
GoG release contains only TSW music (from paragraph 1.). I should refrain from commenting on the matter because I'm not going to buy this game from GoG. Original game releases (by NWC/3DO) could be easily purchased in 1997-1999. It seems difficult to find them nowadays but not impossible.

Changing the music from stereo to midi in the game options seems to change some of the tracks which are played. I've only tested that this changes the main menu and wizard castle music. I'm not sure which soundtracks they're from, just the ones I'm used to.

Sorry for a late response.

It will change them because:
1. GOG uses oggs ripped for a strange gold version/succession wars dics which contain original town screen music as opposed to the POL music. I know that at least in Poland such a version was released with Secret Service Magazine, somewhere around 2000. Still, I think Gold ver should have POL tracks.
2. As opposed to "CD Audio" oggs, the game uses original mid files, thus using the POL music.
3. The midi music lacks a couple of tracks, including 1 battle tune, some terrain (swamp and sea AFAIR), also I recollect that in SW wizard shared town music with some other faction.

Also midi music had a different main menu tune.

There is a "Music Selector" script in the Heroes of Might and Magic 2 folder of standard GoG version. You can choose either original The Succession Wars version or The Price of Loyalty expansion versions of town musics by using this script. Once you make this selection, in-game town musics change permanently. Of course you can always run the script again and make another selection.

How do you do it in the script?

I'm also trying to figure this out as well..

EDIT: Well, assuming that ertugrul refers to the dosboxhomm2_music.conf file in the installation directory, it seems that what it does is simple. It asks "Which town tracks do you want to use in-game?" and depending on your input, it either says
"The game will now use Succession Wars tracks for town music" or
"The game will now use Price of Loyalty tracks for town music"

. The first one is apparently done by, as written in the file, copying the contents \MUSIC\sw to \MUSIC
and the second one by copying \MUSIC\pol to \MUSIC , overwriting the files. Being unable to run this script as a batch file (it gives an error), I just did it manually to change the tracks. Only six tracks are changed in each replacement.

@ertugrul güzel kardeşim, lafı atıp kaçmışsın doğru düzgün açıklasana :) 2019'da hala homm2 sevenleri görmek güzel.

Have a good weekend folks!

OK, here's an update.
I reinstalled the game using the new version with Hotfix (27.05.2019) . Now, the game exe properly shows a DOS menu that allows you to modify DOS configs and music selections. I tested the music selection and it really changes the town music. So, at long last it works well again.

Those of you having an issue, try reinstalling the game with the recent version.

Have a good day folks.