Learn Hardcore Russian: Тихая музыка помогает мне расслабляться вечером. - Quiet music helps me relax in the evening.

Музыка is a feminine noun in Russian (you can see it ends in -а in the nominative singular), so any adjective that describes it must also be feminine, singular, nominative.

masculine: тихий (тихий звук – quiet sound)
feminine: тихая (тихая музыка – quiet music)
neuter: тихое (тихое место – quiet place)

Since музыка is the subject of the sentence and is feminine, you need тихая музыка.

What case is тихая музыка, and what is its function in the sentence?

Тихая музыка is in the nominative singular feminine. It is the subject of the sentence – the thing that does the action.

subject: Тихая музыка
verb: помогает
indirect object: мне
infinitive (what it helps with): расслабляться
adverbial of time: вечером

Why is there no word like “a” or “the” before музыка?

Russian does not have articles like a/an or the. The bare noun музыка can mean:

music
the music
a piece of music

The exact nuance (quiet music, the quiet music, some quiet music) is understood from context, not from a special article word.

Why is it помогает мне and not something like она помогает я?

In Russian:

the subject “quiet music” is expressed by тихая музыка, so you don’t need она.
the person being helped is expressed in the dative case with мне.

The verb помогать normally takes the dative for the person you help:

помогать кому? – мне, тебе, ему, ей…

So:

(Она) помогает мне = (It) helps me
я is nominative (used for subjects), but here “I” am the indirect object, so Russian uses мне.

Why is it мне, not меня?

Меня is the genitive or accusative form of “I”, while мне is dative.

The verb помогать governs the dative case:

помогать кому? – мне, тебе, ему, ей…

So:

Музыка помогает мне. – Music helps me.
Using меня would be ungrammatical after помогать in standard Russian.

Why is the verb расслабляться reflexive (with -ся)?

The verb расслабляться is reflexive because it literally means “to relax oneself”, similar to одеваться (to dress oneself), мыться (to wash oneself).

расслаблять кого? – to relax someone/something (else)
расслабляться – to relax (yourself), to be relaxing

In your sentence, you are relaxing yourself thanks to the music, so Russian uses the reflexive form расслабляться.

Why is it расслабляться and not расслабиться?

This is an aspect difference:

расслабляться – imperfective: process, repeated / habitual action
расслабиться – perfective: a single completed act of relaxing

Your sentence describes a general tendency or habit:

Тихая музыка помогает мне расслабляться вечером.
= Quiet music helps me (in general) to relax in the evenings.

If you wanted to stress a one-time result, you could say:

Тихая музыка помогла мне расслабиться вечером.
= Quiet music helped me (once) to relax in the evening.

Why is расслабляться in the infinitive and not расслабляюсь?

After помогать/помочь, when you say what someone is helped to do, you normally use the infinitive:

помогает мне что делать? – расслабляться

Using расслабляюсь would create a separate finite clause:
Музыка помогает, я расслабляюсь. – that changes the structure.

So the correct construction is:

Музыка помогает мне расслабляться. – Music helps me (to) relax.

In English we say “helps me to relax”. Why isn’t there a word like “to” or чтобы before расслабляться?

Russian doesn’t need a separate word like to to introduce infinitives. Many verbs can be followed directly by an infinitive:

хочу спать – I want to sleep
люблю читать – I like to read
помогает расслабляться – (it) helps (me) relax

Using чтобы would usually introduce a purpose clause, which feels heavier and a bit different in meaning:

Музыка играет, чтобы я расслабился. – The music is playing so that I (could) relax.

Your sentence is more neutral and factual with just the infinitive.

Why is it вечером without any preposition (no в вечером, на вечер, etc.)?

Вечером is the instrumental form of вечер used as an adverbial of time, meaning “in the evening”.

Russian often uses the instrumental (without a preposition) to express when something happens in a general sense:

утром – in the morning
днём – in the daytime / during the day
вечером – in the evening
ночью – at night

So вечером alone already means “in the evening”, and adding в here would be incorrect.

Can the word order be changed? For example: Вечером тихая музыка помогает мне расслабляться?

Yes, Russian word order is fairly flexible. Some natural variants:

Тихая музыка помогает мне расслабляться вечером.
– neutral; focus a bit on тихая музыка.
Вечером тихая музыка помогает мне расслабляться.
– emphasis on вечером (“in the evening…”).
Тихая музыка вечером помогает мне расслабляться.
– slight emphasis on тихая музыка and when it helps.
Мне тихая музыка помогает расслабляться вечером.
– emphasizes мне (for me, personally).

All of these are grammatically correct; the differences are mostly about which part you highlight.

How would I say “quiet music helps me relax in the evenings (regularly)”?

To stress regular, repeated evenings, you can use:

по вечерам – in the evenings (habitually)
вечерами – in the evenings (also habitual)

So you could say:

Тихая музыка помогает мне расслабляться по вечерам.
Тихая музыка помогает мне расслабляться вечерами.

Both sound natural and clearly express a repeated, habitual situation.

How do you pronounce the sentence, and where is the stress in each word?

Stresses:

Ти́хая – ТИ-ха-я (stress on the first syllable)
му́зыка – МУ-зы-ка (stress on му́)
помога́ет – по-мо-ГА́ЕТ (stress on га́)
мне – one syllable, unstressed in the sentence rhythm
расслабля́ться – рас-сла-б-ЛЯ́ТЬ-ся (stress on ля́)
ве́чером – ВЕ́-че-ром (stress on ве́)

Full sentence (with stressed syllables in caps):

ТИхаЯ МУзыка помоГАет мне расслаБЛЯться ВЕчером.

In normal speech, it flows smoothly with a main stress on помога́ет and secondary stresses on тиха́я, му́зыка, and ве́чером.