increasing audio levels in recorded music

Different releases of ABBA’s 1980 song “Super Trouper” show different levels of loudness compared to the original 1980 release.
The loudness war (or loudness race) refers to the trend of increasing audio levels in recorded music, which reduces audio fidelity, and according to many critics, listener enjoyment. Increasing loudness was first reported as early as the 1940s, with respect to mastering practices for