"Loudness War" is a bit of a misnomer and this Wikipedia article is rather incoherent in its treatment of the phenomenon (which is real, but poorly explained here).<p>What controls how loud a piece of recorded music is playing at? The volume knob/buttons (depending on the device); or to put it another way, when you are playing the music for yourself, <i>you control it</i>. If you turn the knob all the way down it will be quiet, if you turn it all the way up, it will be loud. It is therefore trivial to play an album from 1950 louder than an album from 2020: if you want your 1950s jazz record to play louder than your 2020 metal record, the means for doing so is literally at your fingertips.<p>What has actually happened is that the <i>dynamic range</i> of recorded music has decreased. Dynamic range is the difference between the smallest and largest parts of the signal. Audio compressors reduce the peak amplitude of the signal and can also boost the weaker parts of the signal, so the effect is that the parts of music that were musically intended to be quieter start to sound just as loud as every other part in the music.<p>This does not mean that the actual volume of the sound coming out of your speakers is any greater, again, <i>you</i> control that with the volume knob. In fact, I would bet that the end result is that the parts of songs that are musically intended to be the loudest tend not to be emitted at as high a volume as they would be otherwise.<p>The reason for that: if a piece of music has quiet parts (especially at the beginning, as is common in intros), you tend to turn it up. Now that you have increased the total volume, when the loud/energetic part of the song comes on, it will be louder than it would have been had you not turned it up (obviously). If there are not quiet parts, then you never need to turn it up, and you will tend to listen to the music at a consistent level, thus avoiding the peaks of maximum volume that would have occurred had the music had more dynamic range.<p>This is also why this issue is most annoying when you are listening to a range of different music from different eras (e.g. an eclectic playlist), or, when your music is interspersed with ads. You will turn up music that has greater dynamic range, but then a heavily compressed song or ad will come on, and now your volume setting is much too high to listen to it comfortably.<p>Lastly, in terms of why: the louder music is, the better it tends to sound (up to a certain point of course). To really get the full experience of a piece of music, you need to listen to it fairly loud. So in an era of songs with plenty of dynamic range, people could make songs stand out by making them much louder by comparison. Once the dynamic range of everything has been ruined, however, this effect goes away and the end result is what you have today.