Definition of "bar line" []

• A symbol in musical notation used to separate two measures, extended to connect the upper and lower staffs of a grand staff. (noun)

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• "The iambic conductor puffs out his man chest, lifts his batoned hand up, and everybody sees the eighth note hovering there before the bar line on their music stands, and the string tremolo builds, and the mallets of the tympani blur, and the chord swells, and crests, and gets foamy at the ridge, and then the baton comes down and a big green glittering word-wave crashes down on the downbeat."