do you mean to create an Audio track from an existing MIDI-Track? If yes, I would recommend you to create a mixdown with "Separate files for tracks" enabled and reimport the Mixdown of the corresponding track to your project.
If you meant to route the Output of a MIDI-Track into an Audio-Track: No, this is not possible at the moment.
I hope this helps. If I didn't answer your question, please let me know.
Frieder Loch, Software Developer
Steinberg Media Technologies GmbH
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