Adjust the volume
Adjust the volume of music and video
Change the volume for all songs (like turning the volume knob on a stereo): Use the volume slider at the top of the iTunes window.
The maximum volume is limited by your computer’s volume setting.
Adjust the volume of a particular song or video: Select it, choose File > Get Info, click Options, and drag the volume slider. iTunes uses this setting each time the song or video plays.
Have all songs and videos always play at the same volume level: Choose iTunes > Preferences, click Playback, and select Sound Check.
If you’re using remote speakers connected to an AirPort Express: You can use the volume controls on the speakers as well as the iTunes volume controls. To use only the speakers’ controls, choose iTunes > Preferences, click Devices, and select “Allow iTunes audio control from remote speakers.”