You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Adult_contemporary_music

Context:
One big impetus for the development of the AC radio format was that, when rock and roll music first became popular in the mid-1950s, many more conservative radio stations wanted to continue to play current hit songs while shying away from rock. These middle of the road (or "MOR") stations also frequently included older, pre-rock-era adult standards and big band titles to further appeal to adult listeners who had grown up with those songs.

Question:
What does the acronym MOR stand for?

middle of the road