DiTone Audio Unit for Mac

From Music Unfolding:

DiTone splits your input signal into two separate streams. An independent effect is applied to each stream. Then the dry input signal can be mixed into each stream independently. One stream is lowpass filtered and the other is highpass filtered. The two filters are designed to overlap in a nice musical fashion. Finally, the two streams are mixed back together with independent volume controls. DiTone has a variety of effects available including tremolo, vibrato, panning, chorus, and flanger. Altogether, you can choose between twelve different types of effects for each stream and set the parameters independently for each. This gives you a huge array of possible sounds from which you can create incredibly interesting and unique modulation effects.