Trade low end for high end with one control. A tilt runs a low shelf and a high shelf from the same pivot frequency, moving one down by exactly as much as it moves the other up.
Tilt
The tilt runs from -12 dB to +12 dB in tenths. Positive is brighter: the top rises and the bottom falls. Negative is darker.
Half the amount goes each way. At +8 dB the low shelf sits 4 dB down and the high shelf sits 4 dB up, so 100 Hz and 8 kHz end up 8 dB apart. Reading the control as the difference between the ends is what makes it comparable against a shelf on the equalizer.
Pivot
The pivot is where the two shelves cross, from 200 Hz to 4 kHz on a log scale. Frequencies near it barely move whatever the tilt is set to.
Putting the pivot at 250 Hz leaves the bass mostly untouched and turns the control into a treble balance. Putting it at 3 kHz does the opposite: the low and low-mid range does the moving and the top stays roughly where it was.
Tilt vs a shelf
Reach for a shelf when one end of the spectrum is wrong and the other is right. Reach for a tilt when the balance between them is wrong, which is the more common complaint about a finished mix, a recorded lecture, or a transfer from an old source.
A tilt also holds its shape as you move it. Two shelves set by hand drift apart in level as you adjust them one at a time.
Example: a dull phone recording
Pivot 900 Hz, tilt +5 dB.
The low-mid weight that a phone microphone adds comes down 2.5 dB, consonants come up 2.5 dB, and nothing in the middle of the voice moves. A single shelf lifting the top would have left the muddiness underneath it.