http://freemusicsoftware.org/category/free-midi-vst/event-filter This is a collection of cross-platform midi VST plugins
midi16CCRouter - Changes up to 16 CCs to 16 other CCs.
midi2qwerty16 - Use MIDI to trigger fake keystrokes to the focused window.
midiAudioToCC - Converts audio amplitude to CC messages.
midiCCModulator - Use one CC to modulate another CC (or note velocity) in various ways: add/subtract/multiply/etc, plus logic gates (AND, NAND, XNOR, etc).
midiCCReset - Remembers CC values and sends them out again at selected times.
midiCCStepper - Quantize CC events by value or in time.
midiCCToggle - For changing momentary CC buttons into toggles.
midiChannelize - Transforms everything to the selected channel.
midiChs_noGUI - Channel filter/changer like energyXT1 “MIDI chs” component.
midiConverter2 - Change and convert between CC, Channel Pressure, Poly Aftertouch, Program Change, Pitch Bend, NRPN/RPN, and Note On/Off messages in various ways.
midiDelay - Delay notes and/or CCs with feedback.
midiDuplicateBlocker - Remembers all MIDI message values it gets on each channel, and blocks any repeated values until a different value is received.
midiExactDelay - Simple delay (no dry signal, no feedback) with flexible and precise delay time.
midiFingered - Selectively sends standard portamento on/off CC messages to emulate “fingered portamento” for synths that don’t have it.
midiForceToKey - Enforces a scale, and transposes within the scale (optionally based on MIDI notes on a selected channel).
midiForceToRange - Transposes notes by octave into the selected range.
midiInvertNotes - “Mirrors” notes centered around the selected note.
midiKeySplit - Simple keyboard splitter. two versions one splits keyboard into 2 zones and one splits to 4 will try this weekendmidiNotchFilter - Isolate, remove, or channelize specific MIDI messages.
midiNotesToCC - Converts note number and velocity to CC messages.
midiNoteToggle - Notes (optionally within a selected range and/or channel) are toggled… play a note once to turn it on, play it again to turn it off.
midiNRPNConverter - Converts between NRPN/RPN and CC messages, with 16 conversion slots.
midiPolyphony - For spreading polyphony across MIDI channels, i.e. if you play 4 notes, each one will go to a different channel. Polyphony per channel can be set from 1 to 16 notes for more flexibility. You can also use it to convert polyphonic input to monophonic output.
midiProbability - Add probability-based effects to incoming MIDI events, optionally synced to host timeline.
midiProgramChange - Send Program Change and/or Bank Select messages.
midiSimpleLFO - One CC LFO with some “simple” options.
midiSostenuto - Like a piano sostenuto pedal, but for MIDI notes instead of piano dampers.
midiStrum - Sequentially delays notes of an input chord to simulate strumming.
midiStuckNoteKiller - Sends note-off messages to end hanging notes when the host stops (for hosts that don’t do this themselves).
midiSwing - Delays and/or offsets velocity of and applies probability to notes (and optionally also CCs) at every other step of a selected note value.
midiVelocityScaler - Scale/reverse/offset velocity of input notes (Note On and/or Note Off).