Audio is shortform's trend infrastructure: a sound carries a joke format, an editing rhythm, or an emotional register, and thousands of creators pour their own context into it. Tapping a sound shows every video using it, so popular audio functions like a hashtag with built-in instructions.
Creators find trending audio through TikTok's Creative Center, the arrow-up indicator on sounds, Instagram's trending Reels audio surface, and simply paying attention to repeats in their feed. Timing matters — sounds have lifecycle curves, and the window between "rising" and "exhausted" is where the leverage is. Business accounts face licensing restrictions on commercial music, which is why brands often use original or licensed audio instead.