Przed próbą stroimy każdy instrument.

Because przed normally requires the instrumental case when it means before in time or in front of in space.

• dictionary form: próba = rehearsal / trial
• instrumental singular: próbą

So:

• przed próbą = before the rehearsal

This is a very common pattern:

• przed lekcją = before the lesson
• przed koncertem = before the concert
• przed obiadem = before lunch

Here, próba means rehearsal.

Depending on context, próba can also mean:

• attempt
• test
• trial

But in a sentence about tuning instruments, rehearsal is the natural meaning:

• Przed próbą stroimy każdy instrument.
• Before the rehearsal, we tune every instrument.

Stroimy means we tune.

Its basic infinitive is stroić = to tune.

This is the 1st person plural present-tense form:

• ja stroję = I tune
• ty stroisz = you tune
• my stroimy = we tune

In this sentence, it means we tune or sometimes we are tuning, depending on context.

Because in Polish, the verb ending often already shows the subject.

Here, -imy in stroimy tells you the subject is we.

So Polish does not need my unless you want emphasis:

• Stroimy każdy instrument. = We tune every instrument.
• My stroimy każdy instrument. = We tune every instrument.
  (extra emphasis, maybe contrasting with someone else)

This is very normal in Polish.

Because instrument is the direct object of the verb stroimy.

With stroić in this meaning, the thing being tuned goes in the accusative case.

For a masculine inanimate noun like instrument, the accusative singular looks the same as the nominative:

• nominative: każdy instrument
• accusative: każdy instrument

So the form does not visibly change here, even though the case function does.

Każdy instrument means each/every instrument — one by one, individually.

That is slightly different from wszystkie instrumenty, which means all the instruments as a group.

Compare:

• stroimy każdy instrument = we tune each instrument / every instrument
• stroimy wszystkie instrumenty = we tune all the instruments

Both can be correct, but każdy instrument puts more focus on the individual treatment of each one.

Yes, absolutely.

That version means Before the rehearsal, we tune all the instruments.

The difference is mainly:

• każdy instrument = each individual instrument
• wszystkie instrumenty = all the instruments collectively

A learner should notice that Polish often chooses between these depending on nuance, just as English does.

Yes, the word order can be changed, because Polish word order is fairly flexible.

The neutral order here is:

• Przed próbą = before the rehearsal
• stroimy = we tune
• każdy instrument = every instrument

This sounds natural and straightforward.

Other orders are possible, for example:

• Każdy instrument stroimy przed próbą.
• Stroimy każdy instrument przed próbą.

These are all grammatical, but they may shift emphasis slightly. The original sentence is a very natural default order.

Grammatically, stroimy is present tense.

However, in Polish, present tense can sometimes be used for:

• general habits
• repeated actions
• scheduled or typical actions

So this sentence can mean something like:

• We tune every instrument before the rehearsal.
• Before the rehearsal, we tune every instrument.

It sounds like a regular or standard procedure.

A rough English-friendly pronunciation guide:

• Przed ≈ pshet
• próbą ≈ PROO-bom
• stroimy ≈ STROH-ee-mih
• każdy ≈ KAZH-dih
• instrument ≈ een-STROO-ment

A few important pronunciation notes:

• rz in przed sounds like Polish ż
• ó sounds like u
• ą is a nasal vowel; before some consonants, it may sound a bit like om
• ż in każdy sounds like the s in measure

Because każdy means each/every, and in both Polish and English that is followed by a singular noun:

• każdy instrument = every instrument
• not każde instrumenty

So the singular is exactly what you should expect here.

If you want the plural, you would use something like:

• wszystkie instrumenty = all the instruments

Yes.

Przed can mean:

• before (time): przed próbą = before the rehearsal
• in front of (place): przed szkołą = in front of the school

In both uses, it normally takes the instrumental case.

So learners often need to use context to decide the meaning.

It most naturally sounds like a habitual or standard action:

• Before the rehearsal, we tune every instrument.

That is because Polish present tense often describes routine or repeated actions.

But context could also make it refer to a current or near-current situation. For example, if a music teacher is explaining what the group is doing right now, it could still work.

So the sentence is flexible, but without extra context it sounds like a regular practice.