This phone has the ability to run certain applications "in the background". The existing media player does this, and unless this application has been coded to take advantage of this (I'm not sure how easy it is to implement, I'm not sure there is a framework even provided for doing it). Until I know that this exists, It would not be possible for me to disband my original audio player that came with the phone.
This is a feature we intend to offer for phones where multitasking is not intuitive. We don't have an official date for this feature though.
Currently MajiPlayer runs in the background well on most multitasking devices such as S60 devices, I am not familiar with your specific device but there might be a shortcut key to minimize MajiPlayer that you can use.