Какая бы музыка ни звучала, мой брат всё равно начинает петь.

Literally, it is something like Whatever music might be sounding or No matter what music is playing.

This is a very common Russian pattern:

• какой/кто/где/когда + бы + ... + ни
• meaning: whatever / whoever / wherever / whenever / no matter ...

So here:

• какая = what kind of / which
• бы helps create this concessive meaning
• ни reinforces it
• музыка ни звучала = music may be playing / music is sounding

Together, the whole clause means:

• Whatever music is playing
• No matter what kind of music is on

Because какая agrees with музыка, and музыка is the subject of the verb звучала.

In the clause:

• какая музыка ни звучала

the noun музыка is doing the action of звучала (the music was sounding / playing), so it is in the nominative case.

Since музыка is:

• feminine
• singular
• nominative

the adjective/pronoun must also be:

• какая

If it were a direct object, you might see какую, but not here.

In this construction, бы and ни work together as part of a fixed pattern.

бы

Here бы does not simply mean would by itself. It helps form a special indefinite/concessive meaning:

• какая бы... = whatever kind of...

ни

ни strengthens the idea of it doesn’t matter which / no matter what.

So:

• Какая бы музыка ни звучала = No matter what music is playing

You should learn this as a whole pattern rather than trying to translate each word separately.

Other examples:

• Что бы он ни говорил... = Whatever he says...
• Куда бы мы ни пошли... = Wherever we go...
• Кто бы ни пришёл... = Whoever comes...

Because this is not normal negation.

• не usually means not
• ни is often used in set structures like кто бы ни, что бы ни, где бы ни, etc.

Here ни does not mean not by itself. It is part of the pattern meaning:

• no matter what
• whatever
• whoever
• wherever

So:

• Какая бы музыка ни звучала = correct
• Какая бы музыка не звучала = generally wrong for this meaning

A learner should memorize this construction with ни.

This is because Russian uses the past-tense form + бы to build conditional/subjunctive-style constructions.

So although звучала looks like past tense, in:

• какая бы музыка ни звучала

it does not mean simple past was sounding in the normal sense. The whole structure expresses a general idea like:

• whatever music may be playing
• no matter what music is on

This is similar to how Russian uses the past form with бы in other hypothetical or non-literal constructions.

Also, звучала agrees with музыка, so it is:

• feminine
• singular

That is why it ends in -ла.

Звучать literally means to sound. With music, it often means:

• to be playing
• to be heard
• to sound

So:

• музыка звучит = music is playing / music is sounding

In this sentence, звучала is very natural because the focus is on whatever music happens to be on.

A close English rendering is:

• Whatever music is playing...

You could use other verbs in different contexts, but звучать is a very common choice with music, songs, voices, and sounds.

Всё равно means:

• all the same
• anyway
• still
• regardless

In this sentence it shows that the result does not change:

• Какая бы музыка ни звучала, мой брат всё равно начинает петь.
• No matter what music is playing, my brother starts singing anyway.

So the logic is:

1. the type of music changes,
2. but the brother’s reaction stays the same.

That is exactly what всё равно highlights.

Начинает петь means starts to sing, while поёт simply means sings / is singing.

So there is a nuance:

• мой брат поёт = my brother sings
• мой брат начинает петь = my brother starts singing

The sentence suggests that whenever music comes on, singing begins as a reaction. That makes начинает петь very natural.

It emphasizes the moment of starting, not just the fact that he sings.

It sounds like a general habitual statement.

The present-tense verb:

• начинает

often describes something that regularly happens:

• Whenever music is playing, my brother starts singing.

So the sentence is not mainly about one single event. It describes a repeated pattern of behavior.

Because Какая бы музыка ни звучала is a subordinate clause, and it comes before the main clause.

So the structure is:

• [subordinate clause], [main clause]
• Какая бы музыка ни звучала, мой брат всё равно начинает петь.

Russian normally separates such clauses with a comma.

If you reversed the order, you would still use a comma:

• Мой брат всё равно начинает петь, какая бы музыка ни звучала.

Yes, the sentence can be reordered, though the original version is very natural.

Original:

• Какая бы музыка ни звучала, мой брат всё равно начинает петь.

Possible alternative:

• Мой брат всё равно начинает петь, какая бы музыка ни звучала.

Both are grammatical.

Difference in feel

• Putting Какая бы музыка ни звучала first emphasizes the condition/background first: whatever music is playing...
• Putting the main clause first emphasizes the brother’s behavior first.

The original order is probably the most natural if you want the no matter what idea to set up the sentence.

Yes, but it means something slightly different.

Какая бы музыка ни звучала

= Whatever music is playing / sounding

This focuses on the music that is currently on.

Какая бы ни была музыка

= Whatever the music is like or = No matter what kind of music it is

This focuses more on the nature or type of the music, not so much on the fact that it is playing.

So both can work in some contexts, but the original sentence is more idiomatic if you mean whatever music happens to be playing.

Yes, absolutely. It is a very useful pattern.

Common examples:

• Кто бы ни пришёл... = Whoever comes...
• Что бы он ни делал... = Whatever he does...
• Где бы мы ни были... = Wherever we are...
• Когда бы она ни звонила... = Whenever she calls...
• Как бы это ни было трудно... = However difficult it may be...

So the sentence you have is one example of a broader structure that is worth learning as a chunk:

• interrogative word + бы + ... + ни

meaning:

• no matter...
• whatever / whoever / wherever / whenever

That pattern is much more important than this one sentence alone.