Primera.

If you're using ARIA as a VST plugin, you need to record the track as MIDI, not audio. If you want to, you can then render the track to audio by right clicking on the track in the TRACKS window and selecting AUTO CONVERT INDIVIDUAL MIDI TRACK TO AUDIO TRACK.

You can use more than one soft synth if you give them different port numbers - again, right click in the TRACKS window and select PORT.

ROG.