Players are Reason devices that output MIDI notes, either by transforming incoming notes (arpeggiators, chord makers etc) or by generating new notes (sequencers, etc). Normally a Player is attached to a Reason instrument device, but it's also possible to control other instrument plugins:
1. Create an instrument track in Pro Tools and add an instrument plugin.
This is the instrument you are going to control with the Player.
2. Create an instrument track in Pro Tools and add a Reason Rack Plugin as insert.
3. In the rack, open the Browser to the left and click Players.
The Player palette is shown.
4. Drag a Dual Arpeggio device into the rack.
A MIDI Out device is automatically created below the Dual Arpeggio. This makes Reason Rack Plugin send out MIDI notes from the Player.
5. Go back to your first instrument track. In the Instrument section in the track list or Mix view, click the MIDI Input selector and select Reason Rack Plugin MIDI Out. Choose MIDI Channel "All".
6. Record Enable both tracks and play chords on your MIDI keyboard.
The chords go to the Reason track, where the Dual Arpeggio Player turns them into arpeggios and sends the notes back to Pro Tools. The first instrument receives these MIDI notes and plays back the arpeggios.