yes you could
but that would create an extra line of needless code
I'm pretty sure that you need to type the name.
if you need to sort through several tracks, then I'd use an array of all their names
and it would look like
@songs = ["001-Whatever", etc...]
then
Audio.bgm_play("Audio/BGM/" + @songs[i], 100, 100)
where i is the index in the array that you want to play
actually, if you're only looking to play one you can just type in
Audio.bgm_play("Audio/BGM/001-Whatever",100,100)
if I'm not mistaken