Simplify the following text for a Grade 7 native English-speaking person.
Original: During the disco era , many nightclubs would commonly host disco dance competitions or offer free instructional lessons . Some cities had disco dance instructors or dance schools which taught people how to do popular disco dances such as `` touch dancing '' , `` the hustle '' and `` the cha cha '' .
Simplified: People usually dance to disco music at bars called disco clubs .