I seem to only be able to mute the whole track rather than selectively mute a section which I've always done.  Has something changed?
 
Thanks

How are you selectively muting
Has changed since what?
 
Thanks..

Select the clip(s) you want to mute and hit K.

Or you can also automate the volume.

Is this what you're looking for?
http://www.cakewalk.com/Documentation/default.aspx?Doc=SONAR%20X2&Lang=EN&Req=Arranging.37.html
 

stevec
Is this what you're looking for?
http://www.cakewalk.com/Documentation/default.aspx?Doc=SONAR%20X2&Lang=EN&Req=Arranging.37.html
 

In X3 the muted clip icon is no longer there for reasons best known to somebody somewhere.

I was under the impression that the OP wanted to mute by range per the first part of that article.
 

Mute has been replaced by comping.  Open the take lane to show you clip, then select the section to mute to create a separate clip.  Now hit the K key to mute that clip. One nice thing about this approach is you can easily adjust the timing and the fade in/out time to fine tune the muted section.  
 
Check out the video about comping to see this in action.

stevec
I was under the impression that the OP wanted to mute by range per the first part of that article.
 

He may well be, though it's not entirely clear from the question and I wasn't disagreeing with you, just pointing out that the icon no longer shows in case the OP read that part and wondered why the icon wasn't showing.

Ah... good point.