First steps with VSTi instruments in Audition 3

Question

- Switch to multitrack view
- Edit > Audio Hardware Setup - make appropriate settings
- In the "Session Properties" window, ensure that Monitoring is set to "Audition Mix"
- In the Audition menu select "Insert > Midi Track"
- In the midi track's control panel, instead of the usual M S R buttons, you'll see M S L - the last button is for "Live Monitoring" - click it on. 
- Double click on the inserted track, or click on the "Sequencer" button in the track's control panel 
- The first time you do that, the VSTi Plug-in Manager will appear - click on  "Scan" button 
- You should see the three Adobe built-in VSTi instruments listed, and possibly others that are in your Steinberg VST folder, or any folder that you have previously set as containing your VST and VSTi plugins.  Make sure the ones you want enabled are ticked, then click "OK" 
- You should now see a window whose tab probably reads "Sequencer: Midi Track A" - drag its right side until you see three icons at the top right hand corner.  The first looks like a piano keyboard, the second like a piece from a jigsaw puzzle, and the third looks like a bulleted text list.  You can continue to enlarge the window as you wish. 
- On the left of the Sequencer window, you'll see some drop down boxes.  The first is labelled "VSTi: " - click that box and choose Adobe Audition Polysynth. 
- In the next two boxes, select "All" (for the moment). 
- Click on the vertical piano keyboard display just beside the piano roll grid.  You should hear the Polysynth play. 
- Now decide whether you want to use Audition's Virtual Keyboard or an external midi keyboard. 
- To use the Virtual Keyboard, click on its icon - the first in the group at the top right of the Sequencer window.  Click on the virtual keyboard keys - you should hear the notes play. 
- To use your own external midi keyboard, click on the rightmost of the three icons at the top right of the Sequencer window, the one that looks like a bulleted text list.  Select appropriate inputs and outputs.  Play a note on your keyboard and you should hear the Polysynth play. 
- To see the interface for the Polysynth, click on the large Settings button below the Sequencer's M S R buttons.  At the top of the window that appears is a drop down box - click it and choose a preset.  Or twiddle the knobs as you wish. 
- Now read the section in the manual called "Composing with Midi" for further information.

Answer 1

When you mix down a session with midi data in it, the length of the mixdown is determined by the length of any audio data in the session.
If there's no audio data, or the midi data is longer, create a selection of appropriate length and mix down that selection.