Opera combines the art of solo and choral singing, declamation, acting and dancing on a stage before a live audience. Major opera companies in Cambridge hire star singers who attract audience with their power-packed performances. The attraction-quotient for any opera lies with its dramatic musical compositions, consisting of separate recitatives, arias and choruses, ballet, and having a continuous musical structure. Performers are usually the best to reckon in their fields. Opera nights are held five to six times in a week, often running to packed houses. Opera companies collect a huge revenue at the end of each performance, a substantial percentage of which they pay to their performers. YellowPagesGoesGreen lists some of the names of opera companies in Cambridge.