Download and install Chirp Virtual MIDI Keyboard controller (See Resources) by clicking ChripInstaller.zip and running the extracted file. Chirp installs from the Web so an Internet connection is necessary.
Test your Chirp installation by running the software. Click File and select "MIDI Setup" and set your MIDI Output Device to your default sound device. Touch the keys on your computer keyboard to test playback.
Set Chirp's MIDI Output Channel to 1 from the MIDI Setup screen's drop-down menu. Change Chirp's MIDI Output Device to Bus 1.
Select "Always Send Note Data" under Chirp's Preferences tab. Clicking this box allows Chirp to function even when other programs or windows are active.
Run Pro Tools and create a new blank session with a MIDI or instrument track. Set the Pro Tools MIDI or instrument track to receive all MIDI channel data. Depress "Caps Lock" to turn on Chirp.