“I have a radio show on a local community station, and I recently got up the nerve to play a song that our band recorded. What sounded wonderful in the studio, as well as our home and car stereos, and even at the station while cueing up the song, sounded awful over the air. It was very distorted, and the vocals were almost non-existent (like a karaoke version of a song). I realize you don’t know what kind of equipment the station has, and neither do I really. But, is there a certain step of the mixing/mastering process that we might have missed, yet which is required to prepare a song for airplay?”
Yes and no. There’s no specific step “required” for music to be played over the air. However there are a number of techniques that can be employed to help music sound better over broadcast. Some bands do entirely separate mixes of songs specifically tailoring them for the radio. The problem is that what makes a song sound best on the radio often detracts from its sound on a personal stereo. Often the same mix can be used, but with special mastering for the radio. But there’s still a fair amount of music on the radio today that’s identical to the public release, so there are no hard rules here. It depends on budget and how much of a perfectionist those involved want to be. Perhaps we can discuss this in more specific detail in future issues of inSync.
Audio material definitely goes through a number of processes before it is broadcast. Most notable among these is compression (more correctly, limiting). FM stations have to employ very sophisticated limiters that under no circumstances will allow a signal to go beyond a certain level. The way FM works, the signal can’t go beyond a certain defined point or the station will overmodulate and potentially start to bleed into adjacent stations. The FCC does not like this and the fines are stiff. This limiting in and of itself is not a huge problem (though it does depend on the quality of equipment used). The problem arises when people on the front end are turning things up too much (or the equipment is calibrated wrong) and slamming the limiters, which occurs all too often. Depending upon how hard the limiters are being hit they can drastically affect the sound or mix of a recording (your distortion comment indicates this may have been one of your problems). If you can’t give the station a lesson in gain structure, or simply turn it down, a workaround is to remove most of the dynamics (dynamic range) from your music in the mastering process. It’s also a good idea to limit the content of very high and very low frequencies, as these components are usually what trigger most of the trouble. FM can’t transmit above 15kHz anyway, so you can just get rid of that stuff. When all is said and done your music may sound pretty bad on a good system, but you will at least lessen the affect their processing has on it.
There are dozens of other things that can go wrong between your music and the airwaves. Due to variances in radio station equipment and set up, the recommendations above aren’t always necessary and can sometimes even lead to worse results (maybe they aren’t used to levels as hot as what you give them, for example), but most engineers agree that limiting the bandwidth and dynamics of the material reduces the number of potential variables in terms of how it sounds over the air. In your specific case I almost wonder if the deck used to play your material is wired out of polarity (phase) with itself, or if it is in mono and you have applied some process to the vocal track that causes it to disappear under these circumstances. (We’ve had other Tech Tips relating to this phenomenon recently so be sure to check out past issues.) Leaving the mic hot in the DJ booth while listening can also cause this type of problem.