I don’t know why I waited so long to make this video, I had all the material. Now that the ride is closing in I feel guilty and don’t want to see these two and not have done anything.
One thing I understood (a little howto note I post here for later use): in order to balance between music and sound of the video, click-select the music (on the chronology, at the bottom) then press CTRL. Normally the ‘split’ button is active so click on it and voilĂ