As I mentioned above, after `cleaning, etc. merely open the Cowon on your desktop, right click to see the contents in the Cowon, find music folder, then i copy & paste from my ITunes folder (which is of course imported into Itunes at the highest bit rate) straight into the music folder in the Cowon. Close Itunes, close the Cowon, then as mentioned above,
right click and EJECT the Cowon. But be sure you have the BlueHarvest software installed and prior to transferring you re-boot the Mac. Once you EJECT you should be able to enjoy. And when adding other music in the Cowon, do the same thing.
Wish you the best of luck, without a doubt you will love the Cowon, regardless of the model. It does take some certain "understanding' to figure the Cowon out.

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I tried thinking as an Asian, it did little good but It is early here now, but listening to the J3, a classical musical station as I type. Wunderbar !
das va Danya !