Siri on your Mac
You can activate Siri with your voice on your Mac Pro and use Siri for many tasks. For example, you can schedule meetings, change settings, get answers, send messages, place calls, and add items to your calendar. Siri can give you directions (“How do I get home from here?”), provide information (“How high is Mount Whitney?”), perform basic tasks (“Create a new grocery list”), and much more.
Note: To use Siri, your Mac must be connected to the internet. Siri may not be available in all languages or in all areas, and features may vary by area.
Important: Mac Pro doesn’t have a built-in microphone, so you must connect an external microphone (sold separately) in order to use Siri. After attaching your microphone, select it in Sound settings (open System Settings, click Sound, click Input, then select your microphone).
Enable Siri. Open System Settings, click Siri & Spotlight, then set options. If you enabled Siri during setup, press and hold Command-Space bar to open Siri. Or click Siri & Spotlight in System Settings, then turn on Ask Siri. You can also set other options, such as the language and voice to use.
Activate Siri. There are several ways to activate Siri. Press and hold Command-Space bar or click the Siri icon 
in the menu bar (if you selected that option in Control Center settings).
Tip: To learn about more ways you can use Siri, ask “What can you do” at any time, or see the Apple Support article What can I ask Siri?.
Play some music. Just say “Play some music,” and Siri does the rest. You can even tell Siri, “Play the top song from March 1991.”
Drag and drop. Drag and drop images and locations from the Siri window into an email, text message, or document. You can also copy and paste text.
Change the voice. Click Siri & Spotlight in System Settings, then choose an option from the Siri Voice menu.
Learn more. See Use Siri on Mac in the macOS User Guide.