I have two midi tracks, one with piano and another with bass, both on the same midi channel, so that both instruments sounds simultaneously when I play via midi.
I would like to humanize this live playing, inducing a random delay to the tracks while I play.
I wonder if there is a plugin to do this?

So you are using one controller to write MIDI to two tracks simultaneously and you want to make the start time of notes on one or both tracks delayed from the true played time, and you need them done so that the delay is different on each of the tracks and you need to do this in real time so that it works during a live performance?
 
If not, then just apply a randomization to the tracks after they are recorded, and you will have a reversible edit.

slartabartfast
So you are using one controller to write MIDI to two tracks simultaneously and you want to make the start time of notes on one or both tracks delayed from the true played time, and you need them done so that the delay is different on each of the tracks and you need to do this in real time so that it works during a live performance?

Exactly.
I know I can apply the randomization after the midi notes were recorded, but the idea would be that this random delay should be live, since I'm doing a live performance.

The only Humanizing MFX I know of is here http://www.midi-plugins.de/#Plugins

If you're feeling brave and have some basic programming skills, you can create your own. One of the forum members, azslow3, provides an MFX plugin that allows you to write your own MIDI effects using the LUA programming language. He has some pretty powerful presets that demonstrate its capabilities but I don't know if he has a humanize preset for it. He also says on his site (here) that if you want new capabilities to just ask. (Sorry, aszlow3.  )
 
 

kevinwal
If you're feeling brave and have some basic programming skills, you can create your own. One of the forum members, azslow3, provides an MFX plugin that allows you to write your own MIDI effects using the LUA programming language. He has some pretty powerful presets that demonstrate its capabilities but I don't know if he has a humanize preset for it. He also says on his site (here) that if you want new capabilities to just ask. (Sorry, aszlow3.  )
 

Thank you. This is an excellent initiative!
I am also a programmer.
I installed the MFX AZ Lua, inserted some notes on a track and inserted this MFX, I pasted some examples from forum, but it does not seem to be taking effect.
I registered in his forum, but I don't see there how to create a new post.
Anyway, I do not know if there is any incompatibility with Sonar Platinum x64.
 
Do you know how can I solve this?

Did you follow his installation instructions?
From his site:
 
Installation

• Exit Sonar
• Download the installer
• Run installation, modern OS will warn you it is not signed. If you trust me, do not worry. The only "safety" which signed executable gives you is some information about the author and prevention some virus which already exist on your computer to modify the executable. You can find more information about me then you can find in any certificate using DNS of my site. If I start to sign my installators, I will be forced to collect money just for the certificate. And if you already have a virus on your computer, preventing it is too late (also you can compare the size of your local file with the information in the Download section, most modern "viruses" are bigger then my whole package...)
• Several files will be installed and registered for Sonar use. The path is not configurable, but that will not fill your disk. You can uninstall any time, from my knowledge uninstallation is restless
• Start Sonar. "AZ Lua" should appear as possible MFX plug-in (in MIDI tracks FX Bin and Processing menu)Unlike any other MFX plug-ins you have, this plug-in does absolutely nothing till you load Lua program into it. These programs are saved as normal Cakewalk presets and into your project file.To load preset published by other in SPP format:
• Open Cakewalk Plug-in Manager from Sonar Utilities menu
• Select "MIDI Effects", "AZ Lua".
• Press "Import..." buttons, select SPP file and the preset(s) is it, press "Ok"
• Normally imported presets appear is the plug-in presets list without Sonar restart. But sometimes the restart is required

He goes on to say later:

Note: note that changing parameters in the User more does not have immediate effect. Sonar "prepare" MIDI data in advance (there is a setting to change the size of the buffer). MFX plug-in can not "undo" what was already prepared.

Tip: in case you have feeling the preset is no longer working, switch to the Developer mode and check output section. Most probably you will see some "error" there. The problem indicated is NOT with plug-in (you will get Sonar crash then) but with the preset! Presets in AZ Lua are programs, and so they can have bugs.

I did everything.
See the image below.
All scripts seem do nothing.
The script which further demonstrated that something was happening was that (where I have to press C3 in my controller to move the notes one octave).
Played on my controller, all notes sounds, except C3, which is silent.
So I can conclude that the script is running, but is not having an effect on the midi notes that are in midi track.