Ten instrumentalists , three harmony vocalists and ten dancers backed Knowles onstage which also had disco balls hanging from the ceilings and color-changing stairs .

Throughout the tour several incidents happened ; the pyrotechnics meant for the stage injured Bodily_harm two people in the audience , Knowles fell down a flight of stairs during a performance of `` Ring the Alarm '' and had a wardrobe malfunction .

The stage had four video screens , multimedia projectors and a flight of stairs in the middle .