I had loaded 2 songs in wma format,took the memory stick into music store to play on an xs6 . The file shows up on the display,but won't access it.The sales guy said I need to format my USB stick from the yamaha,and then it would play. Anybody familiar with this? Seems it should work,like twiddly bits .Plugged it into a Roland sonic cell,played right off the bat.ideas? help? be blessed