The PSD is very organised to make editing as easy as possible. No layers are merged, which means you can see exactly how it’s all built!
Some information on editing the PSD with Adobe Photoshop:
1) all button layers/groups are marked with red in layers panel for easy switching between pressed, hover (mouse-over) and normal states.
2) the “playlist sliding panel” group is partly masked. To move it up and down, make sure the mask thumbnail (black&white box) is deactivated (doesn’t have a white border around it). To deactivate, just click on the folder icon.
3) glyphs on buttons are marked with green, for example play/pause icons and up/down arrows.
4) the screen colour can easily be edited by double-clicking the layer “screen – colour” thumbnail.