Creating multitrack files with uTool the source files have to be mono wav files.
Click on the “Export” tab, select the “MultiTrack” subtab.
Clcik on the “Add new song” button, click on the folder icon at the top of left tab, then browse the folder where your mono files located.
Drag and drop the mono files from the left tab to the right tab, add name for the song, and save the song.
Now the multitrack song should be appear in the left tab.