Actually I think your first idea is more likely. I don't think the FCC would be concerned about a short gap in a song, or a pause in conversation, or a silent p

Actually I think your first idea is more likely. I don't think the FCC would be concerned about a short gap in a song, or a pause in conversation, or a silent part of a live performance, etc. But commercial program directors are neurotic beasts. And listeners can definitely be fickle! One story I've heard is that PDs obsess over car listeners, who are punching "seek" (or a different preset) at the slightest provocation. They believed that a couple-second silent gap in a song would lose X listeners. They might have even had data to back it up. I've seen song gaps trimmed, or filled with a quick station ID. Philistines!