Can Garage Band play an external MIDI synth?

Can Garage Band play an external MIDI keyboard?

I have an external MIDI keyboard/synth.

In Garage Band Preferences I’ve set Input Device and Output Device to my external MIDI keyboard.

I can play the external keyboard with Garage Band in Record mode and it records just fine.

However, when I select Garage Band to play, nothing plays on the external keyboard.

I can set the Output Device to Build-In Output and Garage Band plays the software synth on my computer just fine.

Can Garage Band play an external MIDI keyboard?

-Mike