Start by creating an instrument device. To get the most out of the Player devices, choose a polyphonic instrument like a piano or synth as these will react best to the signal that the Players send to them. From the Browser, drag a Dual Arpeggio module onto the instrument module you just created, and Reason will connect them automatically. You will now find that playing a MIDI note on your keyboard triggers an arpeggiated pattern which is tempo sync'ed to your project. You can browse the presets of the Arp module to choose a new pattern.
The Dual Arpeggio module has two identical sections that work independently and can be tweaked separately, so the following applies equally to both. Of course you can switch one section off if you prefer. Clicking in the orange line area of the grid will change the length of the pattern in steps, and clicking on the green squares will enter new notes. The blue sliders along the base represent velocity so you can change these to alter the volume of each step. One interesting trick here is to change the direction of the playback, perhaps setting this differently for each of the two sections.
The area to the right hand side of the module contains some interesting controls. At the top is Shift Step, which lets you start playback at a step other than the first, depending on what setting you make. So you can have one arp starting on step 3 for example, and one on step 6. Then there’s Transpose which shifts the key of either arp. Finally Gate Length alters the period of time for which the notes in the sequence are held. When this is set lower you get short, staccato notes, and when set longer you get more sustained notes. Setting these three controls differently for the two stages can yield some cool sounding and unusual results.
It’s worth remembering that as well as turning an arp on or off you can also turn certain characteristics on or off. So in this example the steps are turned on meaning the held note is arpeggiating using the Rate, Octave and Direction parameters. But Pattern is switched off meaning the note pattern is not applied, and Velocity is also off so one standard velocity is applied to every note. You can mix and match these settings for different results, turning some on and others off.
One of the cool things about the Player devices is that you can just keep layering them up like you do with effects! Reason will pass your MIDI input equally to each one and all the active stages will be used to trigger new patterns. You can mix and match devices too, building chains of arpeggiators, scale modules and note echoes for a monster performance.