This is the standard audiophile approach. It adds metadata tags that tell your player how much to adjust the volume during playback without changing the original audio data.
This article will explain what FLAC gain is, why it breaks, and—most importantly—provide step-by-step solutions to fix it for good. We will cover command-line tools (metaflac), GUI applications (MusicBrainz Picard, foobar2000), and best practices for hardware and software players. flac gain fix
Sonos, many Android players (PowerAmp), most high-end DAPs (FiiO, Astell&Kern). Not Supported: Basic car stereos or older smart TVs. This is the standard audiophile approach