Mod to vectrex conversion is not an entirely trivial thing. Here a couple of notes:
←the orginal MOD has 4 voices (later versions can have even more than 4)
→vectrex only as 3 voices
←MODs play samples
→although vectrex can be brought to play samples, it is not its "natural" cause (unlike theg good old Amiga), therefor vectrex will play generated sound after conversion (not samples)
←because MODs play samples there is no way to "auto-map" one instrument (sample) to a PSG setting (something instrument like), since every MOD can have different samples
→not all samples have a "fitting" counterpart in vectrex "instruments".
Therefor:
In order to achieve conversion results which are at least somewhat pleasing, you as a user have to help!
You must tell which of the 4 voices are supposed to be matched to the three vectrex voices
You must tell which of the instruments(samples) of the MOD are mapped to what PSG settings [The vectrex mod-routines use the BIOS sound playing routines]
(This might not be an easy task, since there are two stumbling blocks:
Mod writers often do not name their instruments very descriptive
You have to know how the vectrex sound routines work in order to find settings for "instruments")