An acoustical wall covering assembly (10) with pleats (11) formed and attached in situ to a trim member for covering a wall of a movie theatre, in which a panel (22) of an acoustical wall covering attaches to a pleating member (22) having groups (20) of scores (32, 34, 36, 38) for folding to define the pleats (11). An end of the pleated assembly (10) attaches to a ceiling trim (16). Each pleat (11) is formed and attached in situ to the ceiling trim. Subsequently, each pleat in the attached panel is pulled longitudinally away from the ceiling trim (16) to form an extended pleat in the panel and then secured to a bottom trim (18) to cover a portion of the wall with the pleated assembly. A method of forming and securing an acoustical pleated panel in situ to cover a wall is disclosed.