1. Open your 16 or more tracks midi file into Mobile Music Polyphonic.
2. Click staff sheet button to show staff sheet dialog-box.
3. At Show/Hide item, uncheck all other tracks that you don't want to save into new midi file. Click OK.
4. Now, only these tracks that you check in staff sheet dialog-box are showed. At this time, if you click play button, only these tracks will be played.
5. Now, if you select save as button. Only these tracks will be saved into midi file.