Create MP4 multitrack videos * multiple audio tracks. * premeir pro. * export. * mp4.
Without the video content, here are the most likely ways to "make a piece" depending on what that file contains:
Приложение «Free MP4 Converter - App Store - Apple
If this file is part of the series by Andi Vax, "making a piece" refers to the process of mixing and mastering a track.