Simplify the following text for a Grade 11 native English-speaking person.
Original: Between 1930 and 1933 the German Communists and Social Democrats sang various parodies of the Horst-Wessel-Lied during their street battles with the SA .
Simplified: Before 1933 , the German Communists and the Social Democrats sang parodies of the Horst-Wessel-Lied during their street battles with the SA .