This is actually the EQ section of the famous Elysia Mpressor. With only two controls it's fairly simple to use and sounds quite good: set the center frequency and decide to "tilt" the balance either to the higher or lower frequencies. Boosting the low frequencies automatically cuts the high frequencies and vice versa. Quick and simple.
As the other reviewer mentioned, this is a freeware standalone Mpressor fitler. Its fucking great sounding. Use it all the time for subtle mixing jobs or as an overt effect (try the x10 button). Bit of a CPU hit for how light it is on features, but it has sound quality. Sweep that freq knob around in real time and you do NOT hear aliasing making it ideal for wanking up your samples and stuff. Interestingly its not s much like a LPF/HPF or shelf array but more like a classic 2 band baxandall where sweeping one frequency will always have an audible effect on the other ban and the midrange center. I love stuff like that... like I said, as an effect try x10 mode and assign a midi controller to those nobs to create some whacked out effects.... apply some LFOs to those knobs and prepare for 'broken hifi system' effects although if you do that be prepared to slam it with comrepssion to avoid clipping because you can get some pretty wild volume jumps outta this thing. All in all another very basic 'tilt' kidna EQ that I just love.