Notwithstanding Section 25663 or any other provision of law, persons 18 to 21 years of age may be employed as musicians, for entertainment purposes only, during business hours on premises which are primarily designed and used for the sale and service of alcoholic beverages for consumption on the premises, if live acts, demonstrations, or exhibitions which involve the exposure of the private parts or buttocks of any participant or the breasts of any female participant are not allowed on such premises. However, the area of such employment shall be limited to a portion of the premises that is restricted to the use exclusively of musicians or entertainers in the performance of their functions, and no alcoholic beverages shall be sold, served, consumed, or taken into that area.