Pet Shop Boys + Powerbook

[Dr. Trevor J. Hutley]

I happened to see The Pet Shop Boys playing on a show on BBC 
television last night, and saw that the keyboard player had a 
(Titanium?) Powerbook open right up there in front of him, where you 
might have sheet music positioned, if you were playing from written 
music.  The 'Book and Apple logo were very visible.

I have never seen this before.
WHAT exactly would he be using a Powerbook for ?
(Question to the musician component of this List)

regards,  Trevor