Baada ya kwaya ya watoto kuimba wimbo mpya, watu walipiga makofi kwa shangwe.

Baada ya means after.

In this sentence, it introduces the event that happened first:

Baada ya kwaya ya watoto kuimba wimbo mpya
= After the children's choir sang a new song

So the structure is:

baada ya + event/action = after + event/action

It is a very common Swahili way to introduce a time clause.

The two yas are doing different jobs.

1. In baada ya, ya is part of the fixed expression after.
2. In kwaya ya watoto, ya links two nouns and means something like of.

So:

• baada ya = after
• kwaya ya watoto = choir of children = children's choir

That second ya is a connector used very often in Swahili to show possession or association.

After baada ya, Swahili often uses the infinitive form, here kuimba = to sing / singing, to express the action that happened earlier.

So:

Baada ya kwaya ya watoto kuimba...
literally feels like After the children's choir to sing...

But in natural English, that becomes:

After the children's choir sang...

This is a normal Swahili pattern. English uses a finite verb here, but Swahili commonly uses the infinitive after baada ya.

The understood subject of kuimba is kwaya ya watoto.

So the meaning is:

the children's choir sang

Even though kuimba itself does not show a subject marker here, the noun phrase before it tells you who performed the action.

In Swahili, when one noun describes another noun in the sense of of or possession, the usual structure is:

noun + connector + noun

So:

kwaya ya watoto = choir of children = children's choir

This is the regular Swahili way to express that relationship. English often uses 's or puts one noun before another, but Swahili normally uses the -a connector, here ya.

Because adjectives usually come after the noun in Swahili.

So:

• wimbo mpya = new song
• literally: song new

This is the normal order in Swahili. English usually puts adjectives before the noun, but Swahili usually places them after it.

Also, mpya agrees with wimbo in noun class.

Walipiga can be broken down like this:

• wa- = they (plural human subject marker)
• -li- = past tense
• -piga = hit / strike

So walipiga literally means they hit or they struck.

But in this sentence it is part of the expression kupiga makofi, which means to clap or to applaud.

So here:

watu walipiga makofi = the people clapped

Because watu belongs to the human plural noun class.

• singular: mtu = person
• plural: watu = people

Plural human subjects normally take the verb prefix wa-.

So:

• watu walipiga = the people clapped
• wa- matches watu

This is noun-class agreement, which is a central part of Swahili grammar.

Not literally in the most direct English sense.

Word-for-word:

• kupiga = to hit / strike
• makofi = claps / slaps / applause, depending on context

But as a set expression, kupiga makofi means:

• to clap
• to applaud

So it is best learned as a whole phrase.

Shangwe means something like:

• joy
• excitement
• jubilation
• cheering

Kwa often introduces manner or the way something is done.

So:

kwa shangwe =

• with joy
• joyfully
• enthusiastically
• amid cheers

In this sentence, it tells you how the people clapped.

Yes, it is very natural.

The sentence has two parts:

1. Baada ya kwaya ya watoto kuimba wimbo mpya
   = the earlier event
2. watu walipiga makofi kwa shangwe
   = the main event

So the order is:

After X happened, Y happened.

That is normal in both Swahili and English. The comma also works much like it does in English after an introductory time clause.