This is a cache directory where the MP3 files are decoded when loaded.
You can delete any remaining WAV file here.

Note about MP3 samples: since it takes time to decode them
(the decoding DLL is not the best one) you should avoid them unless
you intend to send your song & its samples over the net.


Credits for the MP3 decoder/player DLL go to
  ISO MPEG Audio Subgroup Software Simulation Group (original DLL)
  Jeff Tsay (DLL modifs)
  Eugene Mayevski (Delphi)