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When listening to a song (either individually or part of a playlist / album) half way through if you select "Start Radio" you are taken to a radio playlist of similar songs, but the original song you were listing to is not included in the radio playlist. When the original song finishes it continues playing from the original playlist / album, and the radio playlist doesn't play unless you select "shuffle play". If you select "start radio" the radio playlist should play at the end of the original song - or at the very least the original song should be included in the radio.