MIDI isn't played stereo in N78

[yapmeo]

A MIDI which downloaded from internet and played on my computer I heard left and right channel have different musical instruments is playing though my earphone, and also Sony Ericsson modern mobile phones like C902 or even K300 K500 or K700 etc.
But NOKIA N78 isn't played stereo, it mixed left and right channel into mono.

How do I solve it?
I found that CorePlayer plays it in stereo!
But not Music Player.


Sample:
Mystic Mysidia from Final Fantasy IV
4Shared >> Mystic Mysidia.mid (Stereo)

Nokia N78-1
v30.011.051.1


Help me please! T_T