Ohh from your link:

Since the NINA Version(??), the files are encoded in ADPCM. Before that, the files use normal PCM.

I have the “Königsedition”. “Königsedition” is the version that’s contains all expansions, equivalent to the English “Creation of a New World” which is also what they sell on GoG. Your link mentions NINA, which must refer to “Neue Inseln Neue Abentuer”, the first expansion, followed by “Im Namen des Königs”. So if Königsedition contains both, it probably also has the ADPCM encoded music.

I also found this comment in the Annozone Forum, where someone found the right codec by trial and error after checking the code of this Anno 2018 reimplementation of Anno 1602. Same ffmpeg command.

He claims adpcm_ima_apc and adpcm_ima_ssi give the same result which seems weird to me. And then further down people discuss that some track still sound weird.

Looking at the ffmpeg code it seems there is one more option that looks quite likely, just beneath adpcm_ima_apc, “ADPCM IMA CRYO APC”, namely adpcm_ima_apm, “ADPCM IMA Ubisoft APM” I’ll try what that gives.