Пусть репертуар и трудный, моя подруга всё равно хочет петь в хоре.

Here пусть is not the usual let-type command.

In this sentence, пусть is a particle that introduces a concession, so it means something like:

• although
• granted that
• even if
• let it be the case that

So Пусть репертуар и трудный... means roughly:

• Even if the repertoire is difficult...
• Granted that the repertoire is difficult...
• Although the repertoire is difficult...

It often has a slightly stronger I admit this, but it does not change the result feeling than plain хотя.

That и is part of a common concessive pattern:

• пусть ... и ..., всё равно ...

It does not mean ordinary and here. Instead, it helps reinforce the meaning:

• even though ...
• granted that ...

So:

• Пусть репертуар и трудный, ...
  = Even though the repertoire is difficult, ...

This pattern is very common in Russian:

• Пусть он и молодой, но очень опытный.
  = Though he is young, he is very experienced.

The и adds a natural concessive emphasis. Without it, the sentence may still be understandable, but this version is more idiomatic.

In Russian, the verb to be is normally omitted in the present tense.

So:

• Репертуар трудный.
  literally: Repertoire difficult meaning: The repertoire is difficult

This is completely normal Russian grammar.

Compare:

• Он студент. = He is a student
• Книга интересная. = The book is interesting

In the past or future, forms of быть do appear:

• Репертуар был трудный. = The repertoire was difficult
• Репертуар будет трудный. = The repertoire will be difficult

Both are possible in Russian, but they are not equally common in all styles.

• трудный = full adjective form
• труден = short adjective form

In modern everyday Russian, the full form is often more natural:

• Репертуар трудный.

The short form:

• Репертуар труден.

sounds more formal, literary, or elevated.

So the sentence uses the more neutral, conversational option.

Всё равно here means:

• still
• anyway
• all the same

It shows that the fact mentioned in the first clause does not change the result in the second clause.

So the structure is:

• The repertoire is difficult, but despite that, she still wants to sing in the choir.

This is a very common combination in Russian:

• Хотя/пусть X, всё равно Y

Examples:

• Хотя холодно, я всё равно пойду.
  = Although it’s cold, I’ll still go.

• Пусть это сложно, мы всё равно попробуем.
  = Even if it’s difficult, we’ll try anyway.

Because хотеть is followed by an infinitive, just like to want to do something in English.

So:

• хочет петь = wants to sing
• хочет читать = wants to read
• хочет поехать = wants to go

This is the normal construction:

• хотеть + infinitive

Russian uses петь because the sentence is about a general activity or ongoing participation, not one completed performance.

• петь = to sing in a general or ongoing sense
• спеть = to sing something through / to sing once / to complete a performance

Here the meaning is:

• she wants to be singing in a choir
• she wants to take part in choir singing

So петь is the natural choice.

If you said хочет спеть, that would suggest something more like:

• she wants to sing a particular piece
• she wants to perform something once

Because в + prepositional is used here to mean in a choir or as part of a choir.

• в хоре = in the choir / in a choir

The noun хор becomes хоре in the prepositional case after в when it means location or being within a group/context.

Compare:

• в школе = at school
• в театре = in the theater
• в хоре = in the choir

So петь в хоре means to sing in a choir.

Yes, there is an important difference.

• петь в хоре = to sing in a choir, meaning to be a choir member / sing as part of a choir
• петь хором = to sing in chorus / all together / in unison

So:

• Она хочет петь в хоре.
  = She wants to sing in a choir.

• Они пели хором.
  = They sang all together / in chorus.

Those are related ideas, but not the same expression.

Yes, absolutely.

A very natural alternative is:

• Хотя репертуар и трудный, моя подруга всё равно хочет петь в хоре.

That is probably the most straightforward way for a learner to say Although the repertoire is difficult...

The difference is mostly one of nuance:

• хотя = plain although
• пусть = granted that / even if / let it be so

So пусть can sound a bit more like:

• Fine, the repertoire may be difficult, but that doesn’t matter

Both work, but пусть carries a slightly more concessive, dismissive-of-the-obstacle tone.

No, Russian word order is flexible, but changing it changes the emphasis.

The given sentence:

• Пусть репертуар и трудный, моя подруга всё равно хочет петь в хоре.

puts the obstacle first, then the main point.

You could also say:

• Моя подруга всё равно хочет петь в хоре, пусть репертуар и трудный.

That version puts the main point first and adds the concession afterward.

The original sentence is natural because it introduces the difficulty first and then gives the stronger result: despite that, she still wants to sing.

Because the first part is a concessive clause, and it is separated from the main clause by a comma.

Structure:

• Пусть репертуар и трудный,
  concessive clause

• моя подруга всё равно хочет петь в хоре.
  main clause

Russian punctuation usually separates this kind of subordinate or clause-like concessive phrase with a comma.

Here репертуар means the set of musical pieces being performed or studied by the choir.

So in this sentence it is something like:

• the choir’s repertoire
• the selection of songs/pieces

It does not just mean a person’s abilities or range here. In a music context, репертуар is the normal word for the body of works being performed.

Both can work, but they are slightly different in feel.

• трудный = difficult, hard
• сложный = complex, complicated

For a choir repertoire:

• трудный репертуар suggests it is hard to perform
• сложный репертуар suggests it is musically complex

In many contexts, both are possible. трудный is perfectly acceptable here, especially if the focus is on the challenge for the singers.