First, you should understand that a 'List' in Poweramp is just a general term for the grouping level of the current playback category - this could be an album, an artist, a genre, folder contents, playlists, etc. Which one is currently in use depends on which Library view you were using when you started playback in the first place (so if you start in Artists view, then a 'List' would be all of an artist's songs). The icon to the left of the song title in the player screen confirms the current pl