Complex sentence: Reactions were mixed; even hippies accustomed to long-form psychedelia like the Grateful Dead were often bewildered by the Arkestra, which included 20--30 musicians, dancers, singers, fire-eaters, and elaborate lighting.
Split into simpler sentences: Reactions were mixed; hippies accustomed to long-form psychedelia like the Grateful Dead were often bewildered by the Arkestra. By this time, the performance included 20--30 musicians, dancers, singers, fire-eaters, and elaborate lighting.