I am using my Xperia E1 as an MP3 player more than a phone. There are two things that I think would improve the Walkman functionality.
1) I have copied across my Windows WMA files as WMA files. These files have "Album Artists" and "Contributing Artists".
When In a Music Album and the songs are displayed, it only shows the "Album Artists", it would be nice to also see the "Contributing Artists". This would be particularly useful in the case of the various artists CD copied across to my Xperia.
2) In the Artists list, somehow pictures have appeared for two of the artists, all the others have the default grey picture. It would be nice to have functionality to add artists pictures, similarly to how you can add album pictures.
