In addition to the techniques for setting media volume in the Sounds settings, you can control the volume of music in the Music app.
Press the phone’s up/down Volume Keys (on the back of the phone). The current media volume is displayed on a slider bar. Continue pressing the Volume Keys to set the volume you want.
Tap the Volume icon (at the lower-left corner of the Playback screen). The current media volume is displayed on a slider bar. Drag the button on the bar to set the volume you want.