This is especially true with opera on DVD but also affects CDs. The singers are clearly recorded in the studio whilst the ambience is recorded outside so the background noises change depending on whether the singers are singing or not. Really irritating.On recording music, that is another mature discipline, it is an interesting one as it is part art and part science. The technical aspects are about engineering but a good recording engineer also needs musical and artistic sensibilities. Good recordings aren't necessarily technically perfect. A lot of my classical recordings date to the 60's (and many are older). These recordings tend to have audible hiss and some technical imperfections but in many cases the recording engineers achieved outstanding results and the resulting recordings still cut the mustard. Mic placement, venue acoustics, recording levels etc were done extremely well even though the technology was primitive compared to that which is easily accessible to amateurs today. On the other hand I sometimes listen to opera recordings where it is like the orchestra and singers are in different venues and with vocals far too forward. And classical music also has issues with remastered music even if it avoided the excesses of the noise war. When I listen to pop things have really gone backwards, I hoped equalising techniques would end the noise war but as that happened a market transition to BT speakers meant material was still compressed so it could be played loudly on BT speakers, car stereos etc.
That said I do think that a mediocre recording of great music is to be preferred over an audiophile recording of music that does nothing for me.
S.