The small a cappella ensemble brought their big guns right away, with each member speaking in rhythm, creating a wall of chatter that in an instant, gave way to raucous polyphonic vocals. After a few iterations, rhythmic spoken word became interspersed with small vocal phrases. The piece was chugging along and it was clear that Roomful of Teeth had a very important message to share with the audience that evening. Roomful of Teeth, the Grammy-winning vocal octet, visited Bailey Hall on Friday night to kick off the Cornell Concert Series 2018-2019 season. The group was founded in 2009 with a goal to explore the expressive potential of the human voice.