How to Tweak iTunes Audio on Your MacBook
Besides the standard volume controls, iTunes offers a full equalizer on your MacBook that you can use to tweak the audio to your liking. An equalizer permits you to alter the volume of various frequencies in your music, allowing you to boost low sounds, lower high sounds, or anything in between.
To open the Equalizer, choose Window→Equalizer or press ⌘+Option+2. Use the leftmost slider (Preamp) to set the overall level. The remaining sliders represent various frequencies that the human ear can perceive.
etting a slider to a position in the middle causes that frequency to play back with no change. Move the slider above the midpoint to boost that frequency; conversely, move the slider below the midpoint to reduce the volume of that frequency.
Continue adjusting the Equalizer sliders until your music sounds the way you like it. In case you prefer to leave frequencies to the experts, the iTunes Equalizer has several predefined settings to match most musical styles.
Open the pop-up menu at the top of the Equalizer window to choose a genre. After you adjust the sound to your satisfaction, close the Equalizer window to return to the iTunes interface and relax with those funky custom notes from James Brown. iTunes remembers your settings until you change them again.