Using Sonar Professional- does anyone know if its possible to automate the gain knob at the top of a midi channel?

Nope, not possible.
 
 

Afraid of that. Thanks, Jonesey.

I believe you can bounce it to an AUX track using live automation.
might not what your looking for though.

It would usful to draw in as it's not midi volume but velocity. You could automate the dynamics of the playing (as opposed to the synths output)

Yes one should not mix the two up,, Volume-Velocity. Even though velocity would seem like a volume envelope it is not so. It is more like the equivalent of hitting or strumming something harder or more aggressively. It does get louder but the timber changes too.

It's been mentioned before, but the gain midi gain knob should really be Volume of the synth. Velocity is not Gain, where as Midi Volume is closer to it. It's still not it as it the output level of a synth, not the input level of the track, but serves the same purpose.
 
But as it is Velocity it would have benefits in being automatable as you don't actually have it in midi itself. Velocity is a note by note control, where as this control affects all the notes velocities

In midi terms, it seems that the Gain knob does exactly nothing, no matter how you set it.   You can watch using a Midi Monitor -- nothing changes when it is moved.    Nor does it appear to have any effect on track envelopes -- they are translated into Midi Control messages exactly the same way regardless of the Gain setting.   (EDIT -- see correction in next comment -- it applies to the Velocity parameter of each Midi NOTE-ON event.  )

williamcopper
In midi terms, it seems that the Gain knob does exactly nothing, no matter how you set it.   You can watch using a Midi Monitor -- nothing changes when it is moved.    Nor does it appear to have any effect on track envelopes -- they are translated into Midi Control messages exactly the same way regardless of the Gain setting.

I think i's a stage between the midi track out and the midi synth in, so is post editing (err fader)
 
Insert AD2 as a Simplle Instrument track.
Press I and select Midi from the track inspector.
Right click the Track and select View> Piano roll.
Enter straight 8th hats,
Turn up an down the gain control in Insepector.
You can both hear the tonal changes of velocity, and see the Vel+ fader on the Trck move.
 
It does work, it's just not Gain.
 
Now in the PRv drop the velocity of the alternate beats (to 64)and hear how they stopped being triggered when taken to zero, when the gain is at -64. It's not scaling from what I can tell but reducing everything by the same amount.
 

Right you are.  Sorry for bad info.   So it applies a fixed (numeric +/- 127) adjustment to the midi velocity for each midi note sent?