Tilt EQ is a free VST Plugin to achieve a linear tilt function with a single knob. This way the spectral balance of audio material can be changed very easily without introducing coloration.
Tilt EQ is based on FIR filters that can be either linear or minimum phase. Baxandall minimum phase IIR filters also have been implemented in order to allow further adjustments. The following graphs show second order Baxandall shelving filters in comparison to the FIR approach with linear slope. The tilt of the slope can be set by the linear tilt knob. The steepness of the slope is given in dB/oct.