Instrumentalists you can recognize after 6 bars..?

How the heck did you arrive on 6 bars? 6 bars? That's and odd marker.

Some guitar players are distinguishable in less than 10 notes? All in the tone/phrasing.

Jazz--Wes Montgomery, Grant Green, Barney Kessel

Blues-The 3 Kings, T-Bone Walker, Buddy Guy

The usual Rock suspects have been mentioned.

World-John Mclaughlin

I like the idea of using six bars to make an assessment of who the performer might be. You're not just hearing the head riff. You're getting a glimpse of the second, as well.

Billy Gibbons 

David Gilmore 

Mike Campbell

Tom Petty 

After six bars I can't even think of my name, let alone my designated driver.

Paul Desmond