Бэк-вокал звучит фальшиво.

Бэк-вокал is a borrowed music term meaning backing vocals, background vocals, or sometimes the backing vocal part.

Depending on context, it can refer to:

• the vocal line behind the main singer
• the backing singer(s)
• the backing-vocal section as a whole

In this sentence, it most naturally means the backing vocals / backing vocal part.

Because in Russian, many newer borrowed compounds with a foreign first element are written with a hyphen. So бэк-вокал is the standard spelling.

This is similar to other loan-based compounds in Russian. The hyphen helps show that бэк- is a prefixed borrowed element related to back.

Звучит is the 3rd person singular present tense of звучать, which means to sound.

So:

• звучать = to sound
• звучит = sounds / is sounding

Since бэк-вокал is treated as a singular subject here, the verb is also singular:

• Бэк-вокал звучит... = The backing vocals sound... / The backing vocal part sounds...

Even though English often uses the plural vocals, Russian can package this idea as one singular musical element.

Because after a verb like звучать you normally use an adverb, not an adjective.

• фальшиво = falsely, off-key, out of tune
• фальшивый = false, fake, insincere, off-key as an adjective

Here the sentence is describing how it sounds, so Russian uses the adverb:

• звучит фальшиво = sounds off-key / sounds false

Compare:

• фальшивый вокал = fake / false / off-key vocal
• вокал звучит фальшиво = the vocal sounds off-key

In this musical context, фальшиво means out of tune, off-key, or not in tune.

The adjective/adverb family фальшивый / фальшиво can also mean:

• fake
• false
• insincere

But when talking about singing, instruments, or musical performance, the usual meaning is off-key.

So in this sentence, a learner should understand it as:

• The backing vocals sound off-key not
• The backing vocals sound fake

It is in the nominative case, because it is the subject of the sentence.

The structure is:

• бэк-вокал = subject, nominative
• звучит = verb
• фальшиво = adverb

So there is no special case ending to learn from this sentence beyond the basic dictionary form of the noun.

Grammatically, it is singular here.

That is why the verb is звучит, not звучат.

Russian can use a singular noun to refer to a musical layer or category as one whole unit. So even if English often says backing vocals, Russian may say бэк-вокал as a singular collective-type term.

If you wanted an explicitly plural version, you could say:

• Бэк-вокалы звучат фальшиво.

That would mean The backing vocals sound off-key in a more clearly plural way.

A helpful stress guide is:

Бэк-вокáл звучи́т фальши́во.

Approximate pronunciation:

• бэк = like English back, but shorter
• вокал = va-KAL
• звучит = zvoo-CHIT
• фальшиво = fal-SHEE-va

A few useful notes:

• ч in звучит is like ch in cheese
• ш in фальшиво is like sh in shoe
• unstressed о is often pronounced closer to a in normal speech

It is natural, especially in music-related speech, reviews, or conversation about performance.

That said, there are also other possible Russian expressions depending on style:

• Подпевка звучит фальшиво.
• Второй вокал звучит фальшиво.
• Бэк-вокалы звучат фальшиво.

Nuance:

• бэк-вокал sounds modern and industry-related
• подпевка is more colloquial and informal
• второй вокал can mean a second vocal part, but not always exactly the same thing

So your sentence is perfectly acceptable.

You could, but it does not mean exactly the same thing.

• Бэк-вокал звучит фальшиво focuses on how it sounds
• Бэк-вокал фальшивый describes the backing vocal as a false/fake/insincere/off-key thing

In music, звучит фальшиво is much more natural when you mean it is out of tune.

So if you want to comment on performance quality, звучит фальшиво is the better choice.

Yes, Russian word order is flexible, but changing it affects emphasis.

Neutral order:

• Бэк-вокал звучит фальшиво.

Possible variations:

• Фальшиво звучит бэк-вокал.
• Звучит фальшиво бэк-вокал.

These alternatives are possible, but they sound more marked or stylistic. The original version is the most neutral and natural for a simple statement.

Russian often softens criticism by using less blunt wording. For example:

• Бэк-вокал звучит не очень чисто. = The backing vocals don’t sound very clean.
• Бэк-вокал местами фальшивит. = The backing vocals are off-key in places.
• Бэк-вокал слегка фальшивит. = The backing vocals are slightly off-key.

A useful extra verb here is фальшивить, which means to sing or play out of tune. So:

• Бэк-вокал фальшивит. = The backing vocals are off-key.

That is a very natural musical comment in Russian.