Yes, I understand now... I tested my official module XM and the option "Amiga Freq.-Table" is enabled.
So, MadTracker 2 uses the option "Linear Freq.-Table" as default... All the modules XM which uses the option "Amiga Freq.-Table" aren't played correctly...
Yannick : Can you improve a best compatibility with "Amiga Freq.-Table" in the next version ? Please don't forget that people (me for example) would like to use their old module XM and improved its to MT2 with MadTracker 2