Go to Settings > Music to set options for Music, including:
Sound Check (to normalize the volume level of your audio content)
Note: EQ settings affect all sound output, including the headset jack and AirPlay. (EQ settings generally apply only to music played from the Music app.)
The Late Night setting compresses the dynamic range of the audio output, reducing the volume of loud passages and increasing the volume of quiet passages. You might want to use this setting when listening to music on an airplane or in some other noisy environment. (The Late Night setting applies to all audio output—video as well as music.)
Grouping by album artist
Set the volume limit. Go Settings > Music > Volume Limit.
Note: In some European Union (EU) countries, iPhone may indicate when you’re setting the volume above the EU recommended level for hearing safety. To increase the volume beyond this level, you may need to briefly release the volume control. To limit the maximum headset volume to this level, go to Settings > Music > Volume Limit and turn on EU Volume Limit. To prevent changes to the volume limit, go to Settings > General > Restrictions.
Prevent changes to the volume limit. Go to Settings > General > Restrictions > Volume Limit and tap Don’t Allow Changes.