Some discussion about the advisability of the "clip" notion for midi has surfaced here from time to time.  
 
As I look more carefully at how clips are made and altered by Sonar, things appear rather peculiar.   Observations welcome on these and other issues regarding midi channel and different types of midi events and different places for entry of the midi event (PRV, EL, Staff, etc). 
 
1)  how does entry of a midi event associated with a different midi channel affect a nearby or overlapping clip? 
 
2)  how does the beginning and end of a clip get extended by entry of a controller value before or after? 
 
Working on some screenshot to show how individual controllers entered into a track create single-event clips .. even when near other clips.  This is in part because of the uncontrolled way Sonar handles midi channels, I believe.

Try this interesting experiment:   create a single controller message in a midi track.   Go to Event List, select the event.   Use "insert" to duplicate the event.    Modify the MBT time stamp for the duplicated event to be way far away from the original time stamp.    Look in track view at the gigantic two-event "Clip" that has been made. 
 
NOW!   Undo.    

New MIDI Events will go into existing clips if they're within a measure of the nearest event; otherwise a new clip is created. I'd have to double-check, but channel assignments generally don't matter in this regard, as the same clip can contain events on any channel. Also if you're working in a track with multiple lanes, you need to take some care because the PRV is not lane-aware, and new events will tend always to go into T1.

 
I just created a midi clip with three notes in it.  Then opened the prv and added a note quite a bit down the line.  A new clip is created for that note.  Add notes in between the two notes and, as long as the notes don't overlap (and always remaining within the first invocation of the prv), a new clip is created for each new note.  What's the logic behind that ?

williamcopper
Try this interesting experiment:   create a single controller message in a midi track.   Go to Event List, select the event.   Use "insert" to duplicate the event.    Modify the MBT time stamp for the duplicated event to be way far away from the original time stamp.    Look in track view at the gigantic two-event "Clip" that has been made. 
 
NOW!   Undo.    

At the risk of helping you hijack another thread... I'm not seeing a problem whether I undo just the alteration of the second event's timestamp or also its insertion. What's the issue?
 
EDIT: Missed that the original post was also yours, so this was not a hijack.
 
 

I may have been wrong about the UNDO, I can't duplicate it just now.   My observation was that the gigantic clip that was created by changing the location of a single event remained after the undo.    But the essential thing:  why should modifying the time stamp of an event create one kind of "clip" .. one stretching thousands of bars ... while entering the same event in a different way creates a different kind of "clip"  .. two tiny ones, side by side, or distant from each other by many bars.  

williamcopper
Try this interesting experiment:   create a single controller message in a midi track.   Go to Event List, select the event.   Use "insert" to duplicate the event.    Modify the MBT time stamp for the duplicated event to be way far away from the original time stamp.    Look in track view at the gigantic two-event "Clip" that has been made. 
 
NOW!   Undo.   

At the moment I can check with X2a only.
 
Second event goes to the same clip, since it is "near" the first one. Then you "move it". Since it is already in the same clip, the clip is extended. Undo works as expected for me.
 
 

williamcopper
..why should modifying the time stamp of an event create one kind of "clip"... while entering the same event in a different way creates a different kind of "clip"

Because moving an event is different from inserting an event. Moving extends a clip and inserting far away creates a new clip.
 
Incidentally, I would not have been greatly surprised if Undo hadn't trimmed the clip; I have run into that before. Yes, I would agree it's a bug when it happens. But no big deal - apply trimming, done.

brundlefly
 moving an event is different from inserting an event. Moving extends a clip and inserting far away creates a new clip.

That is one of those things that sound right, but isn't quite:   one of the fastest ways to create individual non-note midi events (to "Insert" such an event)  is to duplicate an existing one in Event List and then place it at the right spot by Measure:Beat:Tick. 
 
I'm sure someone will now come along and say, "see, you do things in such strange ways it's no wonder you happen upon problems..."

 
Why is it that if I enter a long note which creates a long clip, then shorten the note, the clip is not also shortened ?