Here is a quick cheat sheet on each device you have with links to their user manuals
PitchFactor1. Press and Hold the Encoder and the Right Footswitch for a few seconds to enter System Mode.
2. Turn the Encoder until you see "MIDI" then press the Encoder to select.
3. Turn the Encoder until you see "RCV CH" then press the Encoder to select.
4. Turn the Encoder to select a MIDI Channel number.
5. Press and Hold the Encoder and the Right Footswitch for a few seconds to exit System Mode.
Filter Pro1. Press the MIDI/Sys button to enter MIDI/Sys Mode.
2. Turn the Program Select knob until the display reads "CH"
3. Turn the Speed knob to select a MIDI Channel number.
4. I'm not exaclty sure how you exit... I'd try the MIDI/Sys button again

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M51. Press and hold the Tap footswitch and the Model Select knob to enter Setup.
2. Press the Model Select knob to get to Page 2.
3. Turn the Bottom Left Parameter Knob to select a MIDI Channel number.
4. Press the Tap button to exit Setup.
MPX 11. Press the System button to enter the System Menu.
2. Turn the knob until the screen reads "MIDI".
3. Use the < and > buttons to select the "Recieve" submenu.
4. Turn the knob to select a MIDI Channel.
5. Press the System button to go back to the main System Menu (I'm not exaclty sure what gets you back to the regular ready to rock mode

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