Thank you )
For that timelapse I have used the diaphragm priority mode of my camera. So, only the exposure time was adjusting to the changing light conditions. But, I still had "flickering" on the 17-th second of the video.
If you shoot timelaps at daytime, the best choice will be to use fully manual mode of a camera, with fixed exposure time (longer then 1/30 sec). It will help to reduce flickering.
Another option to handle the exposure changes is to post-process the timelapse sequence in Lightroom, applying the automatic exposure to all of the images.
The freely licensed music is usually present in the youtube clips. If the used music is not free, youtube usually blocks the clip. I have used the SoundHound App to find out the name of interesting music from another timelapse videos on youtube, and downloaded it from the web. The same trick works with the free radio www.di.fm