If the radio station website is making it available for download as an mp3, then it is apparently permitted to be made available for download by the producer in cooperation with the radio station. I don’t see how it should matter whether you keep it intact as one file, as you downloaded it, or break it up into multiple files.
If you weren’t going to buy it otherwise, there’s no issue with hasagas gvul. In any event, any hasagas gvul issue has no bearing whether the producer is maskim or not.