Hi martin,
the keyboard can record while you are playing but it cannot play play back a previous recorded track without stopping the recording function first (either it is midi or audio recording).
The closest I can think of is the chord looper that the SX900 and Genos have to keep your both hands free on the fly for playiong riffs and use easier the pitch bend wheel.
Otherwise on the keyboard we are always programming what the keyboard will play while we are pushing a button(A style part,an audio pad,a midi pad,a midi file) and for more complex stuff we are using registrations.
So for what the guitarist Jhonny A is playing in the video below that Rick has posted.
https://www.youtube.com/watch?v=aj9DxyEJeG800:00-00:30 is our reg 1.Just our left hand is playing the chords on a midi style part or guitar midi pad.
00:31.-00:57 reg 2 our left hand continues to play the chords and uses also the pitch bend wheel for the chords we play with our right hand.
01:33-02:10 reg 3 the style part is playing both the previous 2 guitar sounds that follow our left hand's chords and the right hand is playing the riff.The left hand also controls the pitch bend were is needed.
02:11-02.16 reg 4 there is no sound for the style part,the right hand continues to play the riff and the left hand uses the pitch bend wheel.
02.17- 03.21 reg 5 same as reg 3
03:22-04:15 reg 6 we change the voices for the right hand electric guitars(we can also use a harmony option and definitely dsp effects) .The left hand as always is playing the chords and the pitch bend.
04:16-04:29 reg 7 ending, same as reg 4.
I hope that helps for making an "arrangement" with a keyboard.