Hi, I am probably missing something which is really obvious to others -- after a bit more hunting around the program, the manual and google than i'd expected, I still can't seem to draw in new midi velocity data, as envelopes, controller bars, or any other way.
 
In the piano roll view, I can use the Draw tool to scale existing velocity data, but not to draw in new velocity data (as my reading of the manual now seems to confirm.).(If true, gosh, why?)
 
In the track view, creating automation lanes, I've drilled down into every list and sublist of assignable midi envelope parameters I can find. I see pretty much everything under the sun, but not velocity.
 
Thing is, I'm positive that the other day, in track view, I did see velocity as an envelope assignment as a sub-choice for a midi track, but can't replicate that now.
 
Sorry, I thought this would be an easy one. I've spent most of my learning curve in audio and am only just now getting to midi. A quick steer would be much appreciated!

All notes have a velocity value. There is no such thing as new velocity data without a new note. As you mentioned you can edit velocity. Velocity values "belong" to each note. When you play a note on your midi controller, velocity is recorded along with the note number and timing. CC data is different and so you can draw new CC data in the PRV.

This isn't a Sonar thing. It's just the way midi works. Hope that clear it up for you!

I see, thanks.  I had just assumed that if you could draw in, say, volume envelopes in spaces with no underlying midi data, you could do the same with a velocity envelope -- sending in effect the command, "Ok, when there's no midi data, no harm done, but when there is midi data, play it at whatever is the last velocity stated is."  

Think of it as 1 midi note = 1 velocity
 
you cannot have multiple velocities affecting a single note

A note-on event consists of three bytes. The first has four bits for the command type and four bits for the channel. The second byte specifies the key number, and the third byte specifies velocity.
 
You can't have a note-on event without specifying the channel, key number, and velocity, so the bottom line is velocity cannot exist without a note-on event.
 

"Ok, when there's no midi data, no harm done, but when there is midi data, play it at whatever is the last velocity stated is."

 
Not exactly. As Craig explains, every note has its own velocity value. When you press a key on your controller, a midi message is sent. This message contains the channel, note number, and velocity. The next note will have its own velocity value.

We can put changing dynamic levels on a single note in a VST3 in Cubase.
Can we not create that kind of expression mapping in SONAR?

peregrine
We can put changing dynamic levels on a single note in a VST3 in Cubase.
Can we not create that kind of expression mapping in SONAR?

I assume you mean a single note without affecting other notes playing at the same time. If so, polyphonic aftertouch is ideal for that, assuming the target instrument supports it. 

Thanks for the clarifications, all! Thought I was going mad. (Might be, but that's just not one of the symptons.)
 

There are some tips in here about editing velocity that might be able to give you some transferable guidance/clues:
 
http://music.tutsplus.com/tutorials/7-ways-to-use-and-edit-midi-velocity--audio-2338
 
I stumbled across the site late last night, and ended up looking at probably well over a hundred different helpful quick tip links - techniques for all kinds of recording/editing/mixing/mastering some were for generic knowledge, and some were for particular software, but the concepts were still quite valid for other hardware/software.
 
I found the whole site to bee full of really useful information, so even though I just posted the link for velocity, all the other above stuff might be worth you checking out.
 
Bob Bone