Oprys are the stages (usually with sound systems and audience seating included) -- and the groups of people that organize them -- where both established bands and 'pick-up groups' can perform before an appreciative audience. Admission is low cost. Musicians may make some money through the sale of their recordings, or through 'demo' performances that lead to paid private bookings, but opry performance is for the most part unpaid labor. Bands may be unscheduled, and perform according to a signup sheet or a similar method for organizing the evening's entertainment. Guest bands may be announced in advance for an evening's performance. Unannounced bands may round out the evening. The entertainment may also include back room and outdoor jam sessions, weather permitting. Refreshments are usually also available for sale.