Wimbo wa watoto utasikilizwa na wageni wote ukumbini.

Because the verb is in the passive voice.

In an active sentence, the listeners would be the subject:

• Wageni wote watasikiliza wimbo wa watoto ukumbini.
• All the guests will listen to the children’s song in the hall.

But in the passive sentence you were given, the thing receiving the action becomes the subject:

• Wimbo wa watoto utasikilizwa na wageni wote ukumbini.

So the verb agrees with wimbo, not with wageni or watoto.

It can be broken down like this:

• u- = subject prefix for the noun class of wimbo
• -ta- = future tense, meaning will
• sikiliz- = verb root from sikiliza, meaning listen to
• -w- = passive marker
• -a = final vowel

So:

u-ta-sikiliz-w-a
= it will be listened to

Because the verb must agree with wimbo, which is singular.

A very common mistake is to look at watoto or wageni and expect a plural verb, but those are not the grammatical subject here.

• wimbo = singular
• therefore the verb begins with u-

If the subject were plural nyimbo, then the verb would change:

• Nyimbo za watoto zitasikilizwa...
• The children’s songs will be listened to...

So the agreement is controlled by wimbo, not by the nearest plural noun.

Here wa is the genitive/possessive connector, often translated as of.

So:

• wimbo wa watoto = song of the children / children’s song

This pattern is very common in Swahili:

• noun + connector + noun

Examples:

• kitabu cha mwalimu = the teacher’s book
• nyumba ya baba = father’s house
• wimbo wa watoto = children’s song

The connector changes according to the noun class of the first noun. Here it is wa because it agrees with wimbo.

Not always. This structure can be a little broader than English ’s.

Depending on context, wimbo wa watoto could mean:

• a song belonging to the children
• a children’s song
• a song by the children
• a song associated with children

So context or the provided translation tells you the most natural meaning in a specific sentence.

Because in passive sentences, na often introduces the agent — the doer of the action.

So:

• utasikilizwa na wageni wote
• will be listened to by all the guests

In other contexts, na can also mean:

• and
• with
• by means of

But after a passive verb, na is very often understood as by.

In Swahili, modifiers like all, adjectives, and many descriptive words usually come after the noun.

So:

• wageni wote = all the guests

The word wote comes from -ote, meaning all/whole, and it must agree with the noun class of wageni.

Since wageni is a plural human noun, the correct form is wote.

This noun-first order is normal in Swahili:

• watoto wadogo = small children
• wageni wote = all the guests
• vitabu viwili = two books

Ukumbini is a locative form.

Base noun:

• ukumbi = hall, auditorium, large room

Locative form:

• ukumbini = in the hall / at the hall

The ending -ni is a very common way to express location in Swahili.

Examples:

• nyumbani = at home
• shuleni = at school
• mezani = on the table
• ukumbini = in the hall

So ukumbini tells you where the listening will happen.

Swahili word order is fairly flexible, especially with place expressions.

The version you have is perfectly natural:

• Wimbo wa watoto utasikilizwa na wageni wote ukumbini.

But you may also hear a different arrangement, such as:

• Ukumbini, wimbo wa watoto utasikilizwa na wageni wote.

The meaning stays basically the same, but the emphasis changes slightly. Putting ukumbini first gives more prominence to the location.

The active version would be:

• Wageni wote watasikiliza wimbo wa watoto ukumbini.

That means:

• All the guests will listen to the children’s song in the hall.

Compare the two:

Active

• Wageni wote watasikiliza wimbo wa watoto ukumbini.
• Focus on the listeners

Passive

• Wimbo wa watoto utasikilizwa na wageni wote ukumbini.
• Focus on the song

So the passive is mainly a change in focus and structure.

Because Swahili usually does not have articles like English a and the.

So wimbo can mean:

• a song
• the song

Which one is meant depends on context.

The same is true for the other nouns:

• watoto = children / the children
• wageni = guests / the guests

English needs an article, but Swahili usually does not.

This is a useful vocabulary question.

• sikia = hear
• sikiliza = listen / listen to

So in this sentence, the verb comes from sikiliza, because it is about actively listening to the song.

That is why:

• utasikilizwa = it will be listened to

If the idea were more like be heard, Swahili might use a form from sikia instead, depending on context.