“ The man that hath no musicke in himselfe, Nor is not moued with concord of sweet sounds, Is fit for treasons, stratagems, and spoyles, The motions of his spirit are dull as night, And his affections darke as Erobus, Let no such man be trusted: marke the musicke. ”
 William Shakespeare, The Merchant of Venice (1600). copy citation

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“The reason is, your spirits are attentiue: For doe but note a wilde and wanton heard Or race of youthful and vnhandled colts, Fetching mad bounds, bellowing and neighing loud, Which is the hot condition of their bloud, If they but heare perchance a trumpet sound, Or any ayre of musicke touch their eares, You shall perceiue them make a mutuall stand, Their sauage eyes turn'd to a modest gaze, By the sweet power of musicke: therefore the Poet Did faine that Orpheus drew trees, stones, and floods. Since naught so stockish, hard, and full of rage, But musicke for time doth change his nature, The man that hath no musicke in himselfe, Nor is not moued with concord of sweet sounds, Is fit for treasons, stratagems, and spoyles, The motions of his spirit are dull as night, And his affections darke as Erobus, Let no such man be trusted: marke the musicke. Enter Portia and Nerrissa.
Por. That light we see is burning in my hall: How farre that little candell throwes his beames, So shines a good deed in a naughty world
Ner. When the moone shone we did not see the candle?” source