If you are a 2013 Alt Rock band you don't have to be on Alt Rock radio...but it sure helps. How many Artists become legit Alt Rock radio artists in any given 12 month period? What- a handful? If you take out the random "one hit wonder" type Artists (Capital Cities in 2013, for example.) and concentrate on career-level rock artists, you are maybe talking five new Artists a year.
So let's say you are an Artist with Alt Rock radio aspirations- meaning you want to have the very largest audience for your music that you can possibly have (and be compensated correspondingly.) How do you go from articulating that desire to achieving it.
First, you need to already exist, with a body of work. The idea that a specific Artist will break "on the radio" is as ludicrous a statement in 2013 as saying that they'll break on Dick Clark's American Bandstand. Unless it's a one hit wonder/major label type of situation, bands that make it to Alt Rock radio are already well established in terms of record sales and touring- maybe not spectacularly so, but well established.
Second you need a song that won't cause an average, uninterested listener to change the channel in the first ten seconds. That same song also needs to fit in with the songs already being played on the radio. If you aren't an Artist that fits the initial description and you have such a song, so what. Correspondingly if you ARE an Artist that fits the initial description and you DON'T have a song that fits the description in this paragraph, forget it. You need to have both.
Third, that specific song, from that specific Artist needs to be on an LP that is in a year/two year long promotional cycle, and you need to be touring the record, with a demonstrated degree of success/momentum. All three of these things are must, to have two without the third is as useless as having none of the three.
So let's say you have all three songs: Artist, Song, touring presence. At that point you need to have a representative make your case, and then have the ability to play live shows in the specific station's home market and have those shows sell tickets and be succesful. Then you need to do that two or three times in a row: fulfill all three criteria, preferably with the same representative. This representative will either be someone who works for your manager or your label, and many managers and labels do not have such a person on call.
You need to be able to do it two or three times because competition is so intense that you can fulfill all three criteria and still not "make it" in terms of establishing a last presence on the airwaves. Personally, I think the only viable, realistic strategy is targeting the West Coast tier of Alt Rock radio stations that all happen to be the most sophisticated alt rock stations in the nation (thus affording a "new" act a better shot than at less progressive stations.)
So I'm talking about 91x or 94/9 in San Diego, KROQ in Los Angeles, Live 105 in San Francisco and The End in Seattle. Layered under that are some notable public/university stations that constitute a sub-strata for big-time alt rock commercial radio: KEXP in Seattle, KALX in the Bay Area, KCRW in Los Angeles and then the local NPR affiliates and national NPR. The Southern California/Los Angeles/San Francisco/Seattle market amalgamation represents close to 25 million people.All markets have a strong audience taste for commercial alt rock.
These radio stations also tend to match up their promotional shows so that it is possible for an Artist to play four different radio shows in a week, making it a most efficient combination of potential audience and efficient use of scarce resources. I'm hard pressed to imagine a similar strategy being executed on the East Coast.