I often cite a blog I follow that is written by media researcher Mark Ramsey. He quotes quite a few marketing "gurus" and their takes on the business of radio and other media. Some are better than others. Some are unrelated to rapid technological change or are only peripherally relatable to media.
"You can't create larger audiences by trying to create larger audiences. You can only create larger audiences by trying to get deeper with smaller audiences.
Think about how to get deeper and make more relevant, valuable connections with individuals in a culture or a subculture.
Don't think about audience size. Think about the depth of the relationship and how important it is and how valuable it is. The more you do that, the bigger the audience gets."