Please check the firmware on your device it need to be 83934 if not please update first.

In the uTool click on the “home” tab
Select the LP-16 then the “multitrack songs” and click on the “new multitrack song” at the right tab
In the popup window left tab browse your audio files, then drag and drop to the right side
open your midi file at the right side
Save the song, close the editor
Click on the export tab, make sure the LP-16 selected as target device
Select the song what you created before at the left side
Select your USB drive at the right window, click on the export

Connect the drive to your LP-16 then play back the song

Please let me know if does not working