rhythminmind.net has released 4-Band and 2-Band, which are 100% transparent Four/Two-Band Frequency Divider VST plug-ins for use in modular mixing environments. They split the audio into bands whilst keeping the audio integrity intact. This can be used for frequency dependent FX and mastering purposes. It uses subtractive phase techniques as opposed to minimal phase EQ. In other words the basic signal flow design framework won't change or color your audio.

4-Band and 2-Band function as VST effect plug-ins on Windows and are free.