Despite much concern over the effects of deregulation and competition in the commercial radio industry, no studies have shown empirically how market characteristics, organizational policies, and programmer practices both promote and constrain music programming standardization in the United States. In this article we analyze playlists from a sample of radio stations to develop a measure of music programming standardization, and relate this variable to eight factors identified in the literature as promoting or limiting music programming standardization. Our findings indicate that large markets are the driving force behind music programming standardization, while station ownership is a secondary factor. The effects of these environmental factors on music programming are mediated by organizational policies and programmer practices: low programmer autonomy and the use of audience research and consultants encourage standardization, while an orientation toward new music and the local audience tend to counteract standardization. Based on these findings we argue that, despite increasing ownership consolidation in the commercial radio industry, music programming standardization will likely be confined to larger markets. We further suggest that concentration in the commercial music radio industry will enable small, specialist stations to survive and even multiply so that diversified programming will be available in all market areas.