I'm just adding this thread to add to the google search helpfulness of the forum. I'm not sure if this is specific to X3 but this is the first time I've encountered it.
 
If you create multiple takes in a MIDI track using Sound On Sound mode (and perhaps others) and you open ONE of the lanes in the PRV all the notes of all the takes within that track will appear in the PRV window making it look like you have a pile of doubled notes.
 
This happens even if you mute the lanes no matter what your settings and will also happen if you mute the clips themselves by using Right Click > Clip Mute/Unmute unless you have set the following option in the PRV Views menu View (PRV Menu) > Hide Muted Clips.
 
I found this out after a bit of confusion. I had some live MIDI takes muted, clicked on the one I wanted to work on to open the PRV for that clip and saw a ton of doubled notes. I thought my controller had been sending doubled signals so I was going through deleting some of the doubles and went to audition the part yet some notes were sounding and others weren't I had no idea what was going on and thought the project was screwing up (what was actually happening was I was deleting the notes in the lane that was audible and leaving notes from ones that had the Mute button engaged). I decided eventually to create a new take that I play cleanly and left out certain sections but when I opened the PRV I saw notes in areas where I hadn't been playing at all. I went to through the various Views menu thinking that perhaps the other takes were being shown as well as the selected take and found the View (PRV Menu) > Hide Muted Clips option. I clicked that but the extra notes still remained. So I tried using selecting the muted clips > Right Click > Clip Mute/Unmute option and all of a sudden the extra notes disappeared.
 
So basically it was a lot of confusion and hopefully this will help others not get tripped up the same way.
 
To sum up:
 
If you open the PRV of a specific clip in a MIDI track by double clicking that clip all the notes of all the takes in that track will show up in the PRV creating a grand old mess.
 
Avoid this by:
 
1) Selecting all the clips you do NOT want to edit/view in the PRV
 
2) Hold Ctrl > Right Click > Clip(s) Mute/Unmute (this will mute the clips to make the next option work... you cannot just use the Take Lane Mute button)
 
3) From the PRV menus select... View (PRV Menu) > Hide Muted Clips
 
NOW you will only be looking at the clip/take lane you want to be working on. That last bit may already be set by default (I forget) but it's important.
 
One thing I'm noticing about X3 is some of the default settings are rather weird and I'm having to set things up that I personally feel should be set to more basic parameters. So just be wary of things like this I guess. Great version of the program but it's the little things that'll get you if you aren't paying attention to how the Bakers set things up by default.
 
Hope that helps someone. Cheers.

Muted clips should show ghosted notes in the PRV, making it pretty clear whats active and what's not. But yes, you'll want to make sure Hide Muted Clips is enabled if you're working on a comped MIDI track.
 
You might want to put "Hide Muted Clips" in your title since that's the key to the whole issue.

Good advice, brundle. I will mess with this to see if I can get the ghosted notes but frankly I don't want them because they'll just get in the way of editing. I just found it weird that a) by double clicking a specific clip/take that EVERY clip/take in that track got tossed in the PRV (I'd expect only the clip I want to work on to appear) and b) that the mute button on the lanes wouldn't cause the same behavior as muting the clips but there is probably some editing functionality that is necessary for that is currently eluding me at the moment.
 
It did indeed confuzzle me for a while so thought it should be archived. As far as the title I basically crammed in as many keywords as I could without making the title completely abstract (which could get passed over in searches as irrelevant). Maybe I'll reword it later with better terms.
 
Cheers.

Yes, PRV always shows whole track(s). If it didn't, there would have to be a way to add/remove clips from it (other than by muting). I think that would add more complexity that it's worth. At some point there has to be a difference between tracks and lanes.  If it's really important to be able to isolate clips in that way, they probably belong in separate tracks. But I do think it would be helpful if lane mute also hid clips from the PRV.
 
 

The Comping mode may behave differently (like only the stuff in the parent track is displayed) but I'll have to play with that later. Don't want to meander to far with my current project poking around. What I'm doing now is working and I'm making a pointed effort to actually write/record and pick things like this up as I go as opposed to continuing the obsessive "poke at ALL the things" path I was on the past year. Still a lot of PRV mysteries awaiting me but I know enough now to get things done.
 
Thanks for the extra insight though. Cheers.

THANK YOU

Beepster, thanks for this, that was driving me nuts! 

I'm glad this continues to be helpful. :-)
 
Also note there have been some changes to how Lanes and Comping work in this month's release (Aug 2016). I'm assuming they won't affect this but I haven't tried it out yet.
 
Cheeeers!
 
Edit: I just read the ezine on this month's release. Doesn't look like anything they changed would affect this behavior.

For MIDI I don't use lanes, I just keep each track separate (in the same folder), to avoid having to go through all of this.