How to Adjust Frequencies in iTunes
You adjust frequencies in iTunes using the equalizer. You can adjust frequencies in the iTunes equalizer by clicking and dragging sliders that look like mixing-board faders. The equalizer is shown here.
The horizontal values across the equalizer represent the spectrum of human hearing. The deepest frequency (Daddy sang bass) is 32 hertz (Hz), the midrange frequencies are 250 Hz and 500 Hz, and the higher frequencies go from 1 kilohertz (kHz) to 16 kHz (treble).
The vertical values on each bar represent decibels. Increase or decrease the frequencies at 3 dB increments by clicking and dragging the sliders up and down. You can drag the sliders to adjust the frequencies while the music is playing so that you can hear the effect immediately.