Virtual MIDI port…
On Windows I’ve been using the free loopMIDI driver.
Macs have the ability to create virtual ports within the OS Audio MIDI Control panel.
If you want to send MIDI to another track, AND to a MIDI Device or VSTi plugin at the same time…
You’ll need your MIDI parts on a MIDI track.
MIDI tracks offer up to 4 ‘MIDI Sends’, so it’s possible to send the data to multiple outputs at the same time.
I could set up another track that gets input from the virtual port. It could be a MIDI track, or an Instrument track. In this case I'll make it an Instrument Track hosting a Voltage synth sound in Sonic.
Please be careful with your track INPUTS when using virtual ports. If they are set to ALL MIDI INPUTS, it's possible to end up with feedback situations depending on what tracks you have ARMED at a given moment.
So remember…before you ARM a track for monitoring/recording, you might want to get in a habit of avoiding the ‘ALL MIDI Inputs’ option if you have a virtual ports active.