Good songs do not mystically spread to other stations. Every single song you hear (or every syndicated program you hear) on commercial regular-rotation radio is on that station because of layers of promotion and marketing. The song you hear was the one that made it, it beat out the other 300 songs that were going for adds that week. What you don’t hear are the endless phone calls, faxes, trade ads, personal meetings, consultant recommendations, call-out research, and other things which went into getting the station to add the record. The station owners make it a requirement that DJs make it sound like they picked the music themselves.