MIDI Lab by Soundigy

Plugins
1

I purchased MIDI Lab the other after running the demo version for a while. Pretty flexible. It is available as a standalone, VST plug-in, and AU.
http://en.soundigy.com/midilab.php

2

I use the free PizMidi plugins for complex MIDI processing that GP does not handle natively. They haven’t been updated in years, but they do the job. Very handy! Here is a link to the download archive: https://code.google.com/archive/p/pizmidi/

3

I tried PizMIDI before. I was having issues with them and deleted from all my computers. MIDIKarval has some useful MIDI VST tools; some are free and other are not. Each paid VST plug-in has only function. MIDI Lab is really extensive and yet all are in the same package. All kinds of possibilities.