The sad trombone, often called a fail horn, is a long-running comedy sound effect used to mark defeat, embarrassment or anticlimax. It became especially widespread in internet memes, short-form edits and reaction videos as an easy audio punchline for obvious mistakes. Its staying power comes from how instantly recognizable the descending brass phrase is, even to viewers who do not know any formal source. Online, it fills a similar role to a SpongeBob Fail cue or a quick vine boom, but with a more openly sarcastic tone.