I cannot be the first to spot this but here goes .Just got a Nokia Lumia 620 and a 32 GB SD so I thought I ‘d put a few tunes on the card .That’s when I started to experience the duplicate song files problem that other people have had. Tried all the sync methods windows media player, both win phone apps and copying from folder to folder all bad. Reset the windows media player database re synchronized some songs and it seemed fine .That is until this evening when I see all the artists bar one have disappeared. I reconnect my phone to the PC and the .m4a files are now .wma. Unless for media player converted them when synchronizing but if that is case where did the metadata go?