You can record to multiple software instrument tracks simultaneously.
You can also record to multiple software instrument tracks successively (in Cycle mode) when Show Advanced Tools is selected in the Advanced preferences pane.
Click the Record Enable button in the track header of each track you want to record to. Each clicked Record Enable button blinks red to indicate that the track is ready for recording.
Move the playhead to the point in the ruler where you want to start recording.
Set the metronome for recording, if desired.
Click the Record button 
in the control bar (or press R) to start recording.
Use your MIDI keyboard, Musical Typing window, or onscreen music keyboard to record a part.
Click the Stop button 
in the control bar (or press the Space bar) to stop recording.
A MIDI region is recorded to the selected track. Aliases of the MIDI region on the selected track are recorded to the other record-enabled tracks. Any subsequent edits to the “parent” MIDI region affect all aliases. This is known as layer recording. For details about the difference between layer recording and multiplayer recording, see Recording settings.
To continue playing previous tracks while recording, do one of the following:
Choose Record > Overlapping MIDI Recordings > Cycle Mode On > Create Tracks.
Choose File > Project Settings > Recording, then choose Cycle > Create Tracks from the Overlapping MIDI Recordings pop-up menu.
Control-click the Record button in the control bar, choose Recording Settings from the shortcut menu, then choose Cycle > Create Tracks from the Overlapping MIDI Recordings pop-up menu.
To mute all previous tracks while recording, do one of the following:
Choose Record > Overlapping MIDI Recordings > Cycle Mode On > Create Tracks and Mute.
Choose File > Project Settings > Recording, then choose Cycle > Create Tracks and Mute from the Overlapping MIDI Recordings pop-up menu.
Control-click the Record button in the control bar, choose Recording Settings from the shortcut menu, then choose Cycle > Create Tracks and Mute from the Overlapping MIDI Recordings pop-up menu.