1. You'll need to add one Stereo Aux Input and one MIDI track.

2. Raise the fader on the Aux 1 track.

3. Launch the softsynth plugin of choice.

4. If required by your soft synth, select a patch/instrument. (some softsynths load a default patch, some do not)

5. On the MIDI 1 track, make sure the input says All.

6. On the MIDI 1 track, select the output as channel 1 of your softsynth, which should be listed as an output. (e.g. Sampletank ch1 - 16, or Reason and its various modules)

7. Record-enable your MIDI track. Your softsynth should respond to incoming MIDI messages from your keyboard.

* Please note that Aux Inputs WILL mix down in real-time during a bouncedown, so in most cases, you do not need to make the soft synth into an actual audio track, this will happen automatically when bouncing down.

* You can use multiple MIDI tracks on the same Aux track soft synth- you can send any number of MIDI tracks to one or more MIDI channels within that soft synth.