Which key factor or factors contributed to the rise and growth of rock-and-roll music?

Radio sought a new audience after World War II.

Youths with money were looking for escapism and a new music style to identify their generation.

Desegregation and the beginnings of the Civil Rights movement brought about a blending of black and white cultures in U.S. society.

His contribution to the orchestral genre mainly lies with foreshadowing ideas that are to come like the emergence of the classical symphony, the cadenza for a keyboard, and paired instrumentation;

All of the above have been used in film noir.