rs-met has released Channel Matrix 2×2 and Crossover 3-Way, two freeware VST effect plug-ins for Windows PC.
Channel Matrix 2×2 is a plugin which lets you matrix-multiply the signals of two input channels in order to obtain another two signals which will appear at the two output channels. Example uses are mid/side encoding/decoding, mixing stereo to mono, switching channels left for right, boosting or attenuating signals, inverting signal polarity, etc.
Crossover 3-Way is a plugin to split an incoming (stereo or mono) signal into 2 or 3 frequency ranges (lows and highs or lows, mids and highs). It can be used to build your own multiband effects within a modular (sub)host environment. The band-splitting is done by complementary pairs of Linkwitz-Riley lowpass/highpass filters, the slope of which is adjustable between 12 and 96 dB/oct.