講解：

set the amplifier

設(shè)置揚(yáng)聲器

The machine didn't set the amplifier so we heard nothing.

機(jī)器未開揚(yáng)聲器我們什么也聽不見。

gradually +動詞

逐漸地；逐步地；漸進(jìn)地:

The weather gradually improved.

天氣逐漸好轉(zhuǎn)。

in / out of tune

音調(diào)正確/不正確；演奏合調(diào)/走調(diào):

None of them could sing in tune.

他們中沒有一個(gè)人能唱得合調(diào)。

used to do

(用于過去持續(xù)或經(jīng)常發(fā)生的事)曾經(jīng):

I used to live in London.

我曾經(jīng)在倫敦居住過。

over do it / things

(工作、學(xué)習(xí)等)過分努力:

He's been overdoing things recently.

他最近過于努力了。

prove sth (to sb)

證明；證實(shí):

They hope this new evidence will prove her innocence.

他們希望這一新證據(jù)能證明她無罪。