Over the past 20 yrs. I've seen Rush about 8 times and never did they ever have anyone on-stage with them. I know they use digital sequencers to fill in some of the gaps, but for the most part it's just a three man band.
Alex is soooo under rated only because Geddy & Neil are such stand outs on Bass & Drums respectively. As a former working Bassist I know they are tremendous players. Nothing like watching Geddy hammer notes with his left hand on the neck of the Bass, playing keyboards with his right, playing a set of Bass pedals with one foot, and sing. :shock:
If Aliens do walk among us, Geddy is definitely one of them.