Äänentoisto toimi hyvin myös lavan takana.

Finnish forms compound nouns by joining words together, and they are usually written as a single word.

Here:

• ääni = sound
• toisto = reproduction, playback

So äänentoisto literally means something like sound reproduction, and in context it can refer to the sound system or audio playback/amplification. Writing it as one word is completely normal in Finnish.

The basic verb is toimia, meaning to work, to function, or to operate.

In this sentence:

• toimii = works / is working (present tense)
• toimi = worked / functioned (past tense)

So Äänentoisto toimi hyvin means The sound system worked well.

Because äänentoisto is singular, the verb is also in the singular.

Because hyvin is an adverb, and it modifies the verb toimi.

• hyvä = good
• hyvin = well

So:

• hyvä äänentoisto = good sound reproduction / a good sound system
• äänentoisto toimi hyvin = the sound system worked well

This is similar to English good vs well.

Myös means also, too, or as well.

In this sentence, it adds the idea that the sound system worked well in that place too. So the sense is:

• it worked well behind the stage as well

Its position can slightly affect what feels emphasized. In the given sentence, myös naturally connects with lavan takana, so it sounds like also behind the stage.

Because takana is a postposition, and Finnish postpositions usually require the noun before them to be in the genitive case.

Here:

• lava = stage
• lavan = of the stage

So:

• lavan takana = behind the stage

This is a very common pattern in Finnish:

• talon edessä = in front of the house
• pöydän alla = under the table
• oven vieressä = next to the door

These forms express different location/movement meanings:

• takana = behind, at/in a location
• taakse = to behind, moving to that position
• takaa = from behind, moving from that position

So:

• lavan takana = behind the stage
• lavan taakse = to behind the stage
• lavan takaa = from behind the stage

In your sentence, nothing is moving. It is just describing where the sound system worked well. That is why takana is the correct form.

No, takana is not just an ending added to lava. It is a separate word, functioning as a postposition.

So the structure is:

• lavan
  • takana
• stage-GEN
  • behind

English uses a preposition before the noun: behind the stage.
Finnish often uses a postposition after the noun: lavan takana.

Not completely. Finnish word order is more flexible than English word order, and changes often affect emphasis more than basic meaning.

The original sentence is a neutral, natural way to say it:

• Äänentoisto toimi hyvin myös lavan takana.

You could also say:

• Myös lavan takana äänentoisto toimi hyvin.

That puts more emphasis on behind the stage too.

So yes, the order can change, but the original version is very normal and natural.

Finnish does not have articles like English a or the.

So äänentoisto can mean:

• the sound system
• a sound system
• sound reproduction

Which one sounds best depends on context.

The same is true for lavan: English needs the stage, but Finnish does not use a separate word for the.

Literally, it means behind the stage.

In some situations, English might naturally translate that as backstage, especially if the area behind the stage is what matters. But grammatically and literally, Finnish is just saying behind the stage.

So it is best to understand it first as a physical location, with backstage being a possible context-based translation.