Looks like Maplestory is adding a radio of its own. Included in this 78MB patch file was an 85 minute long MP3. I'm uploading the MP3 to rapidshare as I type this. Of course, with it being from KMST, it's all in Korean, so don't bother downloading unless you understand the language!
Also, with the name of the track being "Aran", I'm sure you can understand the subject matter of the radio for the time being.