Cantamos el estribillo juntos.

Cantamos is the 1st person plural form of cantar, so it means we sing or we sang, depending on context.

Spanish verbs already show who the subject is, so nosotros is usually unnecessary.

• Cantamos el estribillo juntos = We sing / sang the chorus together
• Nosotros cantamos el estribillo juntos is also correct, but it adds emphasis, contrast, or clarity.

Also, cantan means they sing or you all sing.

It can mean either one.

In Spanish, cantamos can be:

• present tense: we sing
• preterite: we sang

You normally tell which one it is from the context.

For example:

• Cada vez que suena esa canción, cantamos el estribillo juntos. = Every time that song plays, we sing the chorus together.
• Anoche cantamos el estribillo juntos. = Last night we sang the chorus together.

Spanish usually uses the definite article more often than English does.

Here, el estribillo means the chorus or the refrain. The article is natural because it refers to a specific part of the song.

So Spanish says:

• Cantamos el estribillo juntos

Even if English might sometimes say We sang chorus together in very informal speech, standard Spanish normally wants el here.

Estribillo usually means chorus or refrain in a song.

A native English speaker may most often think of it as the chorus. In some contexts, refrain is a slightly more precise translation, but chorus is the most natural everyday meaning for most learners.

Because juntos agrees with the people involved.

Here the subject is we, meaning more than one person, so Spanish uses the plural form:

• juntos = together, when referring to a masculine or mixed group
• juntas = together, if the group is all female

Examples:

• Cantamos el estribillo juntos = said by a mixed group or a group of males
• Cantamos el estribillo juntas = said by a group of females

Yes, the position can vary.

The most neutral version is:

• Cantamos el estribillo juntos

But these are also possible:

• Cantamos juntos el estribillo
• Juntos cantamos el estribillo

The meaning stays basically the same, but the focus changes slightly:

• Cantamos el estribillo juntos sounds very natural and balanced.
• Cantamos juntos el estribillo puts together a bit closer to the action.
• Juntos cantamos el estribillo emphasizes together more strongly.

It behaves like an adjective used in an adverb-like way.

That is why it changes form:

• junto
• junta
• juntos
• juntas

Unlike a true adverb, it agrees with the people involved. That is why you say:

• Ellas cantan juntas
• Ellos cantan juntos

So even though English uses the unchanged adverb together, Spanish uses a word that still agrees in gender and number.

Yes. Cantamos juntos simply means We sing together or We sang together.

Adding el estribillo makes it more specific:

• Cantamos juntos = we sing/sang together
• Cantamos el estribillo juntos = we sing/sang the chorus together

No, Spanish word order is usually more flexible than English word order.

Because the verb form cantamos already tells you the subject is we, Spanish can move parts around more easily.

These are all possible:

• Cantamos el estribillo juntos
• Cantamos juntos el estribillo
• Juntos cantamos el estribillo

Some versions sound more natural than others depending on context, but they are all grammatical.

In standard Spanish (including Spain), it is pronounced approximately kan-TA-mos.

The stress is on ta:

• can-TA-mos

A few pronunciation notes:

• c before a sounds like a hard k
• ta is a clear, short syllable
• mos is also short and clean

So the whole sentence is roughly:

• kan-TA-mos el es-tri-BI-yo HUN-tos in many parts of Spain

In Spain, ll in many accents sounds like an English y sound, so estribillo is often pronounced roughly es-tri-BI-yo.