when the PA900 was first released with version 1.0 the inputs worked with both a mic and line in at the same time using the left and right inputs for 2 different things (mic in one and mp3 player in other). Then when 1.01 came out Korg got rid of this feature and only let you do one or the other but not both at the same time. When I questioned Korg Italy I was told that since the owners manual stated you could only do one or the other Korg Japan made them take this feature away for doing both. I suggested they write an addendum to the manual to allow this feature to be implemented again. Now they've listened to me!