Learn Hardcore Japanese: ongaku wo kiku to, sutoresu ga sukosi herimasu. - When I listen to music, my stress decreases a little.

In Japanese, when you use verb (dictionary form) + と to mean “when / whenever / if [someone] does X, Y happens”, the verb before と must be in plain (dictionary) form, not in ます-form.

So:

音楽を聞くと、ストレスが少し減ります。 ✅
音楽を聞きますと、ストレスが少し減ります。 ❌ (sounds wrong / unnatural in everyday speech)

You can still mix plain and polite forms inside the same sentence:

Clause before と: 聞く (plain form required by the grammar pattern)
Main clause: 減ります (polite ます-form)

This is completely normal in Japanese. The politeness level is determined mainly by the final verb form of the sentence (here: 減ります), so the whole sentence is polite.

What does 〜と do here? Is it “and”, “when”, or “if”?

In this sentence, と connects 音楽を聞く and ストレスが少し減ります with a meaning like:

“When I listen to music, my stress decreases a little.”
“If I listen to music, my stress decreases a little.”
“Whenever I listen to music, my stress decreases a little.”

This verb (dictionary form) + と pattern often expresses:

A natural consequence / automatic result
- 春になると、暖かくなります。
  When it becomes spring, it gets warm.
Regular, habitual results
- このボタンを押すと、ドアが開きます。
  If/when you press this button, the door opens.

Your sentence is the second type: a general rule or typical effect. It implies this always or usually happens when you listen to music.

What’s the difference between using と here and using 〜たら or 〜ば?

All three can be translated as “when / if”, but they have different nuances:

〜と (dictionary form + と)
- Often used for natural, automatic, or habitual results.
- Suggests whenever X happens, Y always happens (almost like a rule).
- Your sentence:
  音楽を聞くと、ストレスが少し減ります。
  → Whenever I listen to music, my stress (always / generally) goes down a bit.
〜たら (past plain form + ら)
- More casual and flexible; used for once X happens, then Y.
- Can describe one-time events or future conditions.
- 音楽を聞いたら、ストレスが少し減ります。
  → When I (have) listened to music, my stress goes down a little.
  (Feels more like a specific time, or “after I listen”.)
〜ば (仮定形 conditional)
- Conditional “if”, can sound a bit more formal / logical.
- 音楽を聞けば、ストレスが少し減ります。
  → If you listen to music, your stress decreases a little.
  (Has a slightly more “theoretical” or explanatory feel.)

In context, と is a natural choice because it suggests a regular effect of listening to music.

Why is 音楽 marked with を and ストレス marked with が?

This reflects the roles of the nouns in the sentence:

音楽を聞く
- 音楽 is the direct object of 聞く (to listen to).
- を marks the thing being listened to.
- Literally: listen to music.
ストレスが少し減ります
- ストレス is the subject of the verb 減ります (decreases / goes down).
- が marks what undergoes the change described by the verb.
- Literally: stress decreases a little.

Put together:

音楽を聞くと → When (someone) listens to music
ストレスが少し減ります → stress decreases a little

So を marks the object of 聞く, and が marks the thing that changes with 減ります.

Could we use は instead of が in ストレスが少し減ります? What would change?

Yes, you can say:

ストレスは少し減ります。

The difference is nuance:

ストレスが少し減ります。
- が introduces ストレス as the subject that is undergoing change.
- It answers the question “What decreases a little?” → Stress does.
- Feels neutral, like presenting a fact.
ストレスは少し減ります。
- は makes ストレス the topic: “As for stress…”
- It can contrast with something else:
  - As for stress, it goes down a little (maybe something else doesn’t).
- Often feels more like you’re talking about stress in contrast to other things.

In isolation, both are understandable, but ストレスが少し減ります is the more straightforward “stress decreases a little.”

Who is the one listening to music and feeling less stressed? There is no subject like “I” or “you”.

Japanese often omits the subject when it is clear from context.

In 音楽を聞くと、ストレスが少し減ります, the subject is not stated, but could be:

I (the speaker)
you (general “you”, like “people”)
people in general

Depending on the context, it might be interpreted as:

When I listen to music, my stress decreases a little.
or
When you listen to music, your stress decreases a little.
or
When people listen to music, their stress goes down a bit.

Japanese doesn’t need to say I / you / people unless it is necessary to avoid confusion. The listener understands from the situation who it is about.

What nuance does 少し add? How is it different from ちょっと?

Both 少し and ちょっと can mean “a little / a bit”, but their feel is slightly different:

少し
- A bit more neutral or formal.
- Works well in written Japanese, explanations, polite speech.
- ストレスが少し減ります。 → My stress decreases a little.
ちょっと
- More casual / conversational.
- Often used in spoken language.
- ストレスがちょっと減ります。 → My stress goes down a bit. (more colloquial)

In this sentence, 少し matches the relatively neutral/polite tone of 減ります.

Why use 減ります instead of just saying なくなります or 減る?

Each verb has a different nuance:

減る / 減ります
- Means to decrease / to go down.
- Implies there is still some stress left, just less than before.
- ストレスが少し減ります。 → Stress decreases a little.
なくなる / なくなります
- Means to disappear / to be gone / to run out.
- Implies stress goes down to zero.
- ストレスがなくなります。 → The stress disappears.
減る vs 減ります
- 減る: plain form.
- 減ります: polite ます-form, which matches the polite tone of the sentence.

Your sentence wants to say stress is reduced a bit, not completely gone, so 少し減ります is the natural choice.

Why is 聞く written as 聞く and not 聴く? Aren’t both read as きく?

Yes, both 聞く and 聴く are read きく, but they have slightly different nuances:

聞く
- General “to hear / to listen”, including simply hearing sounds.
- Commonly used for listening to music too, especially in everyday writing.
- Simpler, more common kanji.
聴く
- Emphasizes actively listening / appreciating (e.g., carefully listening to music).
- Often used in more literary / expressive contexts, song lyrics, etc.

In ordinary sentences, 音楽を聞く is perfectly natural and very common.
音楽を聴く is also correct, with a nuance of more attentive, focused listening. Both are fine; 聞く is just the default.

Could I say 音楽を聞くとストレスが少し減る in casual speech?

Yes.

音楽を聞くと、ストレスが少し減ります。
- Polite: 減ります (ます-form).
音楽を聞くとストレスが少し減る。
- Plain / casual: 減る (dictionary form).

In casual conversation with friends, 減る is natural.
With someone you should speak politely to (teacher, boss, stranger, etc.), 減ります is better. The grammar with 〜と stays the same; only the last verb’s politeness level changes.