It seems quite impossible, to import a song composed in tuxguitar, and exported via midi (BTW the only way to export something half way audible) to be arranged in LMMS.
Yes the notes are there, but I have to reassign instruments again to have it sound like in TuxGuitar.
I am using LMMS0.4.6 & TuxGuitar1.2 and LMMS complained it needs a soundfont, which i did not found. Problem is, that the assignment of the instruments is gone. Especially for percussion stuff. I would've hoped there is a way without having to reassign instruments.
And where am I supposed to find soundfonts that work with LMMS. All I found were labeled soundfonts, but LMMS couldn't read them.
(Well MIDI was also supposed to be a "standard"... :-( )
Well it seems that LMMS is not importing program changes from midi files. but you will get more help at LMMS forums, since we can't fix this problem from tuxguitar side.