I had the same problem when I first started. What I do is use File/Render to render just the TRKS track. Click the “S” solo button on TRKS (assuming you are not rendering stems) and then render. Then in Magma make sure you use the rendered wav file. Make sure you have the volume up as it should be and the rate of the track is set to 1.0 since it will render it using whatever settings you have in effect at the time.
You are about to leave Rhythm Gaming World and access the external songs DB. While no song or file sold for commercially available videogames is hosted there and only fan generated content is allowed, Rhythm Gaming World has no direct control over the database and no files are hosted here. Alright, we had to made you aware of this, now you can visit the database!