Pink Floyd were among the first bands to use a dedicated travelling light show in conjunction with their performances. During the Barrett era, dynamic liquid light shows were projected onto enormous screens behind the band while they played, and the band also incorporated large numbers of strobe lights, which were controlled manually by an engineer. This had the effect of totally obscuring the band itself, except for their shadows, which Barrett took advantage of: he would hold his arms up during parts where he was not required to play, making his shadow grow, shrink and undulate, adding to the visual spectacle. They developed many of these lighting techniques through their fortuitous early association with light artist Mike Leonard.