pure pitch

When it is struck, a tuning fork produces an almost pure tone, retaining its pitch over a long period of time.

音叉被敲击时，产生几乎纯质的音调，其音量经久不衰。

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The clear, pure light of the morning made me long for the truth in my heart, which alone could make me pure and clear as the morning, tune me up to the concert-pitch of the nature around me.

早晨的纯洁之光，使我的心渴慕真理，惟有这种仰望真理之心，能使我纯洁如早晨，使我和周围的自然交响乐和谐合拍起来。

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