Audio production and performance.
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Low-frequency content below 80Hz from vocals, guitars, and cymbals is inaudible but consumes headroom and triggers bus compression prematurely. Standard mixing practice: HPF vocals at 80-100Hz, acoustic guitars at 100-120Hz, cymbals at 200-500Hz. Reserve sub-80Hz exclusively for kick drum and bass. Reference: Bobby Owsinski, The Mixing Engineer's Handbook.