Translation:Turn the music volume down so it won't disturb the neighbors.
Music volume sounds really unnatural. "Turn the volume down" or "Turn the music down" are both ok but they don't sound right together
The sentence also does not even say volume.
声音 is sound or voice. 音量 is volume.
So it is wrong in both languages...
That isn't necessarily true. A lot of devices that output sound have different sound output levels (including windows past version 7) so you could have a sound output and a voice output, in which case the precision would be applicable and not awkward.
There is no verb in the first statement, so it's not a demand, and there is no 如果, so it's not a hypothetic.
I don't underatand how this is acceptable Chinese...
因果关系 (because..so...) is sometimes expressed as in this sentence, without conjunctions; but more importantly, English doesn't allow strings of grammatically unconnected clauses like Chinese does, so "so" has been added here to make the English correct. (I'll admit I was slightly baffled myself when I first saw this sentence, not sure whether Duo wanted a subordinate phrase or just a semicolon!)
As to the lack of verb, Chinese predicates do not necessarily require one, but the wording given does sound slightly awkward. I would have gone with a "把"字句 like "请把音乐放小一点". Your "请降低音量" is acceptable as well.
What makes me confused is the word “不会”, which makes this sentence sound like a mild advice, rather than a request. The translation closer to the sentence: If you turn down the music volume a bit, then it won't disturb the neighbors.
If you replace 不会 with 不要, it will sound more imperative.
I think "Turn the volume down a little, don't disturb the neighbors" is good English, isn't it? I mean there are ways to link two ideas without conjunctions, just like in Chinese.
"Lower the sound of the music, so it won't disturb the neighbors" should be accepted.
can you turn down a volume in english? this may be too much nonsense even for english!.