LG CU500

According to the manual, you can switch from playing music to other tasks by hitting the left soft key (minimize). In playing around with this, the only time I can get this soft key is if I select All Songs, and start playing from the first one selected by the phone. If I select a playlist, or if I skip down a couple of songs to start the play, the minimize key does not show up, and is not functional.

Am I doing something wrong, or is this a bug.