Context: ReplayGain is a standard for measuring and storing the loudness of an MP3 file (audio normalization) in its metadata tag, enabling a ReplayGain-compliant player to automatically adjust the overall playback volume for each file. MP3Gain may be used to reversibly modify files based on ReplayGain measurements so that adjusted playback can be achieved on players without ReplayGain capability.

Question: What is the name given to the standard for measure and storing the loudness of an MP3 file?
Answer: ReplayGain

Question: What is measuring and storing loudness of an MP3 file also known as?
Answer: audio normalization

Question: What does the standard ReplayGain allow a player to automatically adjust?
Answer: the overall playback volume

Question: What program can be used to modify files based on ReplayGain measurements?
Answer: MP3Gain

Question: MP3Gain is important because it allows players without what capability to have adjusted playback?
Answer: ReplayGain capability