How to Keysound easy. It is so easy that any other method is stupid.

Needed software :

You need a finished song. You need a midi file for that same song Song.midi should contain all your tracks.

On Be-Music Helper, create a new project and select your .midi song. Select the track you want to start with. Create a new division. Leave everything as default.

Ok the idea here is to be able to separate all the notes on this track so you don't have a million wav files for the same note. 

Write the midi file and call it trackXX.mid. Insert it in your favorite DAW software with the right track so that it sounds normal. Export the track in wav format.

Now open woslicer and drag the newly created trackXX.wav into it. Make sure it is the correct BPM, so that your notes will not become shorter or longer (RIP if the BPM changes). Press B then M press ok...

The next step is the "Transpose to..." button. It is used to define your wav files. Start with 01. Let's say you have 20 wav files with trumpet_0XX. Your next piano_0XX instrument should start with the 21st line. If you don't know the slot of your next instrument, open uBMSC and look at the note labels (1G: Trumpet_001.wav). This is not just a number make sure it's set to the right one!!!

In uBMSC, click on the first empty line in the note label section. Select all your instruments_0XX.wav and drag them into the note label section.

Go back to bmhelper and click on Copy BMS Data to Clipboard, go back to uBMSC, make sure you are at the beginning of the bms and paste.

Repeat for all tracks.

Enjoy your keysounded BMS. Now chart it properly!