If it's at too low a volume it's not been properly mastered.
There are a bundle of things you can do:
Almost any free wav. editor will allow you to "normalise" the file - take it to max available vol given the dynamics of the file.
That's not a great option.
Almost any recording software will allow you to increase the volume, faux master, throw a limiter across it etc etc to make it louder. You could go back & remix an increase volumes of each track/group etc.
I've attached an MP3 of the track (I recorded it from your web page - has some glitches in it that I had to fix - may have been the download process) run through a "Normaliser" that uniformly lifted the volume.
There are a few other things you'd be better off doing before you lift the vol.
View attachment val.mp3
You'll note that the norm didn't do much. It lifts as much as it can buut only as much as the loudest part will allow & the track has a few loud moments that prevent this doing much.
Some gentle compression to reduce the peaks & lift the rest would help or remix & ride the faders a bit more on those loud bits!
