There was a news that Disciple 1 and 2 got flac soundtrack that can be bought separately but I don't see it anywhere.
static.gog.com/news/update_gogcom_blog_flac_soundtracks

It was mp3-to-flac lossy from music torrents.
Almost all OST on GOG is LOSSY. Almost all of them is GameRIP lossy. Some of FLAC is based on gamerip too.

True lossles OST only for _some_ indie-games and Witcher series (but it can be low-quality too --i not check and dont trust indie-devs).

Проверьте рутрекер. Хотя там по моему тоже нет флак, зато где-то указывалось где искать тот самый флак, с которого GOG сделали свою lossless OST.
Не всё то, что заявлено как LOSSLESS им в действительно является. И даже AidoCD не всегда на самом деле AudioCD (например Half Life или GTA 1\2 на торрентах (любых)).

Oh well. Thanks anyway I guess.

Они зарелизили ФЛАК обратно. Это тот же архив 2014 года с апконвертом. Отсутсвует почти копия genbrief (winfgen) и credits трек. Оный же файл в MP3 - битый (только пол трека). МП3 тоже апконверт.

Для 1-ой части тоже вернули. На качество и битость лично пока не проверял.

If the file structure of Disciples 1 is the same as in the Steam version, the soundtrack is just in the "music" folder, as raw wav files, though. That's obviously also lossless.

A lot of it is just general sounds and noises, though. From what I can see, the actual music is:

BATLTRCK.WAV
CAMPTRCK.WAV (note: this is just a fragment of MKINGSL.WAV)
MDEADWS.WAV
MENUTRCK.WAV (note: this basically MKINGSL.WAV with heavier drums)
MGOLDEN.WAV
MKINGSL.WAV
MMIDGARD.WAV
MUNSPOKN.WAV (The most memorable music, imo)

UNDETRCK.WAV also has some rhythm in it, but it's mostly noises.

Yes, mostly AMBIENT for games isn't AMBIENT music, but sound. For Disciples 2 GOG exclude ambient tracks, for Disciples 1 include for no reason. Ambient tracks - ambient sounds, environment sounds. For D2 its amb00... tracks, for D1 its AMBIENT00... tracks.

Both game have music in WAV in game folder.

There are a couple more to be found in the .smk videos. Bink Tools had issues converting them (even though it's literally its own file format), but I managed to convert them fine using VLC's "Convert/Save" function.

In Disciples 1, the two videos containing clean music are:

Briefing\DEFAULT.SMK - The briefing video music
Video\CREDITS.SMK - The credits music

Of course, the audio in the SMK files is compressed, so converted versions of these will not exactly be pristine... but it's the best we got.

Anyway, I went ahead and compiled it all, putting the menu and briefing tracks at the front and the credits at the end to frame the remaining tracks. I left out the "Camp" track though, because it's really just a 15-second fragment of "King".

So here it is: the "Disciples: Sacred Lands" flac soundtrack, in the cleanest quality available:

https://www.mediafire.com/file/mz6zfkllafign36/Disciples_1_-_Sacred_Lands_%28flac%29.zip/file

For Disciples II, depending on the version, the files might be packed in .vpk archives. They can be opened with a tool called GCFScape.

The files inside pretend to be wav but actually use some kind of mp2 compression. Again, VLC could convert them for me.

After extracting VPK files are 100% identical to retail 2.02\3.01 versions. What compression, or what conversion needed? It just differ quality for differ files. Genbrief or something else.

SMK is old bink format. Even bnk files are not identical to other bnk files. Most RAD Tools versions not compatible for each other, not backward too. Same for binkw32.dll: if it differ than video bnk version - video or audio not played.
Mostly for video track. With audio tracks some other soft\tools can be useful, just like you did with VLC. I just use VLC to play SMK files "as is" - it work for audio tracks, and not work for video. Discipels 2 bnk files opened in VLC play both video+audio.

<Briefing\DEFAULT.SMK>
O! Im forgot about this file. I remember only credits video music.