Lǎoshī zài yǔyīn kè shàng ràng wǒmen xiān liànxí shēngdiào, zài liànxí jùzi.

在 here is a preposition meaning “at / in / during”.

The structure is:

• 老师 在 语音课 上 …
  = The teacher (在) during / in phonetics class …

In Chinese, you normally mark the place or time of an action with 在 + place/time. So:

• 老师在语音课上让我们…
  literally: The teacher, during phonetics class, has us…

Without 在, you can still say:

• 语音课上老师让我们…

This is also correct, but now 语音课上 is more like a topical phrase (“In phonetics class, the teacher has us…”). Using 在 is the most straightforward way to mark the location/time of the action.

In 语音课上, 课上 functions like “in class / during class”.

• 课 = class, lesson
• 上 here is not a verb; it’s working like a postposition meaning “on / in / during”.

Compare:

• 桌子上 – on the table
• 书上 – in the book
• 课上 – in/during class

Don’t confuse 课上 with 上课:

• 上课 (verb phrase) = to have class / to attend class
• 课上 (noun + postposition) = during class / in class

So 在语音课上 ≈ “in phonetics class / during the phonetics class.”

Both are grammatical and very natural:

1. 老师在语音课上让我们先练习声调，再练习句子。
2. 在语音课上，老师让我们先练习声调，再练习句子。

The difference is only in emphasis:

• Version 1 starts with 老师, so it emphasizes what the teacher does in that class.
• Version 2 starts with 在语音课上, so it first sets the scene (in phonetics class), then tells what the teacher does.

In everyday speech and writing, both orders are common; there’s no real change in meaning.

让 is a causative verb here. It roughly means “to have (someone) do something”, “to tell/ask (someone) to do something”, or “to make (someone) do something” depending on tone and context.

In this sentence, 老师让我们… most naturally means:

• “The teacher has us do …”
• or “The teacher tells us to do …”

It doesn’t focus on “permission” the way English “let” often does; it’s more about giving instructions / arranging what students should do.

The pattern is:

X 让 Y + Verb Phrase

Meaning: “X causes/has/makes Y do (something)”

Applied to this sentence:

• 老师 – the one causing the action
• 让 – causative verb
• 我们 – the ones who actually perform the action
• 先练习声调，再练习句子 – the actions

So:

• 老师让我们先练习声调，再练习句子。
  = The teacher has us first practice tones, then practice sentences.

This pattern is very common and productive:

• 妈妈让他做作业。 – Mom makes/has him do homework.
• 公司让我去北京出差。 – The company is sending me to Beijing on a business trip.

先…再… means “first…, then…” and explicitly shows sequence of actions.

• 先练习声调，再练习句子。
  = First practice tones, then practice sentences.

先…然后… also means “first…, then…”. In most everyday contexts, 先…再… and 先…然后… are interchangeable:

• 先吃饭，再/然后看电影。
  = First eat, then watch a movie.

Subtle tendencies:

• 再 after 先 is very common in instructions / classroom language, sounding crisp and step‑by‑step.
• 然后 sometimes feels a bit more narrative / storytelling, but it’s also fine in instructions.

So here, 先…再… is the most natural pattern for describing classroom procedure.

The comma separates two sequential actions, each with its own verb:

• 先练习声调，
• 再练习句子。

Using 和 (“and”) would mean you are grouping the objects together for one action, not doing them in two steps.

Compare:

1. 老师让我们先练习声调，再练习句子。
   – First practice tones (step 1), then practice sentences (step 2).

2. 老师让我们先练习声调和句子。
   – First practice both tones and sentences (as one combined task).
   – This also sounds incomplete without saying what happens after “first”.

So in the original sentence, the comma plus 再 is needed to clearly show two separate, ordered actions. 先练习声调和句子 is grammatical as a phrase, but it doesn’t express the same “step 1 / step 2” meaning.

You must repeat 练习 here.

• 先练习声调，再句子 is ungrammatical, because 句子 is a noun and needs a verb.

In Chinese, it is very natural (and often required) to repeat the verb when you have two parallel actions:

• 先看书，再写作业。 – First read, then write homework.
• 先复习生词，再背课文。 – First review new words, then memorize the text.

If you really wanted to avoid repeating 练习, you’d have to change the structure more drastically, but in normal speech you simply repeat it: 先练习A，再练习B.

Chinese does not mark tense the same way English does. This sentence by itself is time‑neutral. Depending on context, it can mean:

• “In phonetics class, the teacher has us first practice tones, then practice sentences.”
  (a general description of what usually happens)
• “Yesterday in phonetics class, the teacher had us first practice tones, then practice sentences.”
• “Tomorrow in phonetics class, the teacher will have us first practice tones, then practice sentences.”

The tense is usually indicated by:

• Time words: 昨天 (yesterday), 现在 (now), 明天 (tomorrow), 每次 (every time), etc.
• Aspect particles: 了, 过, 着
• Modal verbs / future markers: 会, 要, 打算…

Since none of these appear here, we read it as a general / habitual description unless context tells us it’s about a particular time.

Chinese uses measure words when you specify number or quantity:

• 几个句子 – several sentences
• 一些句子 – some sentences
• 三十个句子 – thirty sentences

But when you talk about an action in general, without focusing on how many, you can just use a bare noun:

• 练习句子 – practice sentences (in general)
• 练习发音 – practice pronunciation
• 学汉字 – learn Chinese characters

In this sentence, the emphasis is on the type of practice, not on how many sentences, so 练习句子 without a measure word is perfectly natural.

Both relate to pronunciation, but the nuance is different:

• 语音 – phonetics/phonology, the sound system of a language
• 发音 – pronunciation (how you actually pronounce)

So:

• 语音课 = a phonetics / sound system class
  – sounds more formal / academic, like a course in Chinese phonetics.
• 发音课 = a pronunciation class
  – sounds more practical, focusing on how students pronounce.

In many real-life teaching situations, a teacher might casually say 发音课, but 语音课 is very common in textbooks and course descriptions and fits well here.

They all relate to sound, but refer to different things:

• 声调 – tones (specifically the lexical tones in languages like Mandarin).
  Example: Mandarin has four main 声调.

• 声音 – sound / voice in general.
  Example: 你的声音很小。 – Your voice is quiet.

• 音调 – pitch / intonation / musical tone.
  Often used for music or overall pitch contour, or more generally for “tone” in a non-technical sense.

In a Mandarin class where you’re practicing the four tones, 声调 is the precise, standard term.

Location/time phrases like 在语音课上 are quite flexible. Common, natural positions include:

1. 老师在语音课上让我们先练习声调，再练习句子。
   – The teacher, in phonetics class, has us…

2. 在语音课上，老师让我们先练习声调，再练习句子。
   – In phonetics class, the teacher has us…

You could also say:

3. 老师让我们在语音课上先练习声调，再练习句子。

But this version slightly suggests contrast like “the place where we do this practice is in the phonetics class (as opposed to somewhere else)”, which is a bit less neutral in this context.

So (1) and (2) are the most straightforward neutral options. Chinese usually puts 在 + place/time:

• either right after the subject,
• or at the beginning of the sentence as background information.

They are homophones (same pronunciation, different characters and meanings):

• 在 (zài, fourth tone) – preposition / verb meaning “at / in / to be (located) at”.
  Example: 老师在语音课上… – The teacher is in phonetics class…

• 再 (zài, fourth tone) – adverb meaning “again / then / further / and then”.
  In 先练习声调，再练习句子, it means “then / next”.

How to tell them apart:

• In listening, you rely on grammar and context:
  • After a subject and before a place/time: probably 在.
  • Between two actions in a “first…, then…” pattern: probably 再.
• In reading/writing, you just learn their characters and meanings; they are not interchangeable.

So in this sentence, 在 marks location, while 再 marks sequence.

Both 让 and 叫 can be causative: “to have / make someone do something.”

• 老师让我们先练习声调。
• 老师叫我们先练习声调。

Both are understandable and grammatically correct.

Nuances:

• 让 is more common and neutral, especially in standard Mandarin and written Chinese.
• 叫 can sound more colloquial and, in some contexts, a bit stronger / more like “order”.

In a textbook-style sentence about a teacher’s instructions, 让 is the more typical and neutral choice.