Speed variations in a turntable,phonograph, or cassette player that cause irritating flattening in pitch with sour notes (wow) and/or garbled notes with jerky sharpening in pitch (flutter). Often heard from poorly manufactured, old, or poorly-maintained audio equipment. In the ages when LPs and audio cassettes were the only audio media available, stereo/high-fidelity magazines often used to rate audio components with wow and flutter specifications ranking at the top of the list.