The sad trombone has been a comedy shorthand for failure for decades, long before it became a staple of online video. Brass players used the descending wah-wah phrase to puncture a boast or mark a losing moment in variety shows, cartoons, and game shows, and the gag translated easily to short clips and memes. Creators now use it whenever a plan collapses, a prediction proves wrong, or a dramatic build-up leads nowhere, because the sound alone tells viewers the outcome was a letdown.