it forwards any data received from the game boy, without consistency check or conversion. so, if properly formatted midi data are received, it should work. if it's random other data, the midi driver or other software layers might crash.
i don't know about lsdj's midi out. does it really send midi bytes?

the commands might differ between the win and mac version. I only have the mac version here.
Also I never tested it with LSDJ only with Nanoloop and there it all works like a charm.

Basically if you want to sync the GB to your computer, you start nlmidi with the -sync option, so Nanoloop with receive the MIDi clock, the in Nanoloop you just set the tempo to External and there you go.

the -midi option is for progs like mGB where you want to send actual notes to the Game Boy (afaik this also works with LSDJ)

Oh. I assumed it was for lsdj midi out.

it doesn't do anything because there is no program on the game boy that sends MIDI.
the command only exists for the possibility that one day there might be a midi sequencer on the game boy.

Yes. In the nlmidi04 command line tool it tells you to use "-MIDIRECEIVE" to send midi from the gb to the pc.  That must not be correct so I will try "-GETMIDI" instead.

Oh and of course there is also the -receive / -send parameter that you can use to load or download data from the cart, but that doesn't have anything to do with MIDI

well it depends what you want to do, do you want to send midi from the GB to the computer?

It must be a typo in the nlmidi04 program usage text then. I'll try getmidi tonight.

Afaik there is no -MIDIRECEIVE command.
check the manual here: http://www.nanoloop.com/midi/midi.html

it's either -midi or -sync or you can use -getmidi to send midi to the computer from the GB

It's the setting for midi to go from the gameboy to the pc.  It looks like on the nanoloop site it's referred to as "-getmidi" so I'll try that command when I get home tonight.

what is "-MIDIRECEIVE"? i never heard of a different mode...what are you trying to do?

I want to set my nlmidi adapter to "-MIDIRECEIVE" but the command doesn't do anything.  Other permanent and non-permanent settings seem to work fine (-midi, -MIDI, -sync, and -SYNC).  I'm using the most recent nlmidi04 that was zipped with the 1.7 update.