Março é o mês em que eu pago a inscrição do curso de música.

It literally means in which.

So o mês em que eu pago... is literally the month in which I pay...

In natural English, we would usually say the month when I pay... or just the month I pay....

A common pattern in Portuguese is:

noun of time + em que

For example:

• o dia em que = the day when / the day on which
• a semana em que = the week when / the week in which
• o mês em que = the month when / the month in which

English often uses when, but Portuguese often uses em que in this structure.

Learners often want to do that because English uses when, but o mês em que... is the more natural and safer choice.

O mês quando... may be understood, but it is not the usual standard pattern here.

If you want to sound natural, use:

Março é o mês em que eu pago...

In informal Brazilian Portuguese, yes, many people do say o mês que eu pago...

But em que is the more complete and standard form.

A good way to see it is this:

• basic sentence: Eu pago a inscrição em março.
• relative clause version: Março é o mês em que eu pago a inscrição.

The preposition em stays there when março turns into o mês.

Because month names are often used without an article when you are simply naming the month.

So:

• Março é o mês...
• Abril é mais quente.
• Janeiro foi tranquilo.

That is normal Portuguese.

In some contexts, especially in speech, you may hear articles with months, but here no article is the expected choice.

Yes, month names are normally lowercase in Portuguese:

• janeiro
• fevereiro
• março

Here Março has a capital M only because it is the first word of the sentence.

If it appeared in the middle of a sentence, you would normally write março.

Yes, it can be omitted.

Portuguese often leaves out the subject pronoun when the verb form already shows who the subject is:

• eu pago
• or simply pago

So this is also correct:

Março é o mês em que pago a inscrição do curso de música.

Including eu is still completely natural in Brazilian Portuguese. It can add clarity or just reflect everyday speech, where subject pronouns are used quite often.

Because the present tense in Portuguese is often used for:

• habits
• routines
• general facts
• scheduled events

So this sentence suggests something like a regular fact: March is the month when this payment happens.

It does not have to mean only right now.

If you wanted to make it more explicitly future, you could say:

• Março é o mês em que vou pagar a inscrição...
• Março é o mês em que pagarei a inscrição...

But the original sentence sounds more like a normal recurring situation.

Inscrição usually means registration, sign-up, or enrollment.

In a sentence with pagar, it often suggests the registration fee or the payment connected with registering.

So it is different from things like:

• mensalidade = monthly fee / tuition payment
• matrícula = enrollment, registration, sometimes very similar depending on context

The exact English translation depends on the situation, but inscrição is basically the registration/enrollment step.

Because Portuguese usually contracts de + o into do.

So:

• de + o = do
• de + a = da
• em + o = no
• em + a = na

That means:

a inscrição do curso de música

literally contains:

a inscrição de o curso de música
but Portuguese contracts that to do.

Literally, it means course of music.

In natural English, you would usually say:

• music course
• music class
• music program

depending on the context.

The pattern curso de + subject is very common:

• curso de inglês = English course
• curso de dança = dance course
• curso de música = music course

It links the course to its subject.

So de música means of music or more naturally in music / music-related.

This is one of the most common ways Portuguese describes types of courses, areas of study, and categories.

The ç is called cedilha, and it makes the letter sound like s before a, o, or u.

So Março is pronounced roughly like MAR-soo in Brazilian Portuguese.

Without the cedilla, marco would sound with a k sound: roughly MAR-ko.

So the ç is important for pronunciation.