LBA are files from Little Big Adventure. The game uses one set of MIDI files with different instrument banks for OPL2 (SAMPLE.AD) and OPL3 (SAMPLE.OPL).
LOSTVIK are files from The Lost Vikings. The MIDI files differ between OPL2 and OPL3 as well, hence the two directories.
To play an example file, go into the directory containing the XMI file you want to play (example: title.xmi), then in DOSBox, type "..\XPLAY title.xmi ..\SBFM.ADV" for OPL2 (SBFM.ADV will automatically use SAMPLE.AD) and "..\XPLAY title.xmi ..\SBP2FM.ADV" for OPL3 (SBP2FM.ADV will automatically use SAMPLE.OPL).
Thanks for those files, I have checked out that, and, I had many bugs in reading/write of AIL (I had the inability to read LOSTVIK banks, and I had damaged save result) which now I finally fixed. The one thing I need to complete - banks toggle (to toggle 128-instrument sets by combo-box rather showing everything like done for BNK files). I have plan to implement own format I will use for libADLMIDI which will support everything supported by existing bank formats with the ability to provide full GS or XG standard instruments set to have properly played of MIDI files are designed for those standards (include a support of custom percussion channels providing by those standards).
I have updated build, now editor must support any AIL banks correctly

Next update will have "banks" combo-box and list will show 128 instruments maximum
EDIT: "next update" has been implemented, and now bank editor supports 128-instruments banks: adding/removing/clearing, and ability to switch between AdLib BNK mode (I.e. show all instruments in same list without dividing by banks)