Just tested one of the short melodies from "free-vgms", and indeed, the music is not looping.
Maybe it's a non-looping VGM? I'll have to take a look at that later.
I just used vgmcheck to test it: https://www.smspower.org/forums/12009-VgmcheckExtractLoopAndTimeInformationFromV...
I took a look at both "Actraiser - Fillmore.vgm" (from SGDK examples) and "golf.vgm" (from "free-vgms") and those were the results:
D:\Pessoal\Util\vgmcheck-2.0>vgmcheck "Actraiser - Fillmore.vgm" --Raw VGM information-- Total samples: 2275559 Total time in mm:ss: 0:51.60 Loop start: 17639 Loop start in mm:ss: 0:00.40 Loop time: 2257920 Loop time in mm:ss: 0:51.20 --Usage in SSBB-- (.brstm conversion) New loop start: 28672 New loop end: 2286592 D:\Pessoal\Util\vgmcheck-2.0>vgmcheck golf.vgm --Raw VGM information-- Total samples: 1693440 Total time in mm:ss: 0:38.40 Loop start: 1693440 Loop start in mm:ss: 0:38.40 Loop time: 0 Loop time in mm:ss: 0:00.00 --Usage in SSBB-- (.brstm conversion) New loop start: 1705984 New loop end: 1705984
It seems that "Actraiser - Fillmore.vgm" has a loop set up on it, while "golf.vgm" does not have a loop. (it's loop time is zero)
It looks like in order to use "golf.vgm" in a loop, it will be necessary to edit it in order to explicitly define loop ponts on it; please see: https://vgmrips.net/wiki/Manual_looping_tutorial