Midi Slide, Portamento, Legato.

I don't know what this thing is called officially, but what I want to do is: When I trigger a new note in the midi editor before the previous note is released, instead of cutting off the previous note and starting another note, it just takes the old note's voice to the pitch of the new note. I can do this this automatically with the SI-Bass when i put it to Mono.
How can I do this same thing let's say with the Rapture Session Saxophone?
Do I have to turn it to mono and how do I do that?
Please give me your guidance, I really need to figure this one out.
-Jonne

Does Rapture not have a monophonic option? I thought all synths did. Although some don't label it as such - some have a "maximum notes" or "max polyphony" setting.