Hello I have a question about "Import Midi" 

 I tried to import my midi file into BIAB, previously I had arranged well for 4 tracks (Drums, Bass, Melody, Guitar) but without Solo on Intro & Interlude part. I successfully imported it to BIAB's Melody track. 
 My purpose is to add Realtrack phrase on Intro & Interlude 'cause I think it's cool, but still need to preserve all MIDI parts which I created... 
 But why I only heard only one track (the very top track in SEQ) played when I playback the Melody track? I did assign it in Melody/Multi(16): 
1st trial : Ch-1 Drum; Ch-2 Bass; Ch-3 Melody, Ch-4: Guitar) --> only Drum is heard (not really drum sound, then I assigned it to Ch-10)
2nd trial : Ch-2 Bass; Ch-3 Melody, Ch-4: Guitar, Ch-10 Drum) --> only Bass is heard this time. 

 I checked the below link in Youtube but I cannot get the result as it did , what's wrong with that? (If you think Re-channeling is the solution but why I heard Ch-2 playing in 2nd trial 
    
https://www.youtube.com/watch?v=OejFpi4TjIQ 

Thanks in advance.