When satellite radio was launched several years back, providers XM and Sirius crowed that they would fill the void left by increasingly consolidated corporate radio, featuring formats and genres virtually ignored on the terrestrial dial. And for a while, that’s exactly what they did. But lately, Sirius and XM have begun to sound suspiciously alike. More alarming is the fact that each service has been quietly dropping music formats that fail to garner a large audience – exactly the sort of pandering to the masses that satellite was supposed to alleviate.