時間をかける彼女 (excerpt #1)

This might be more popular as "The Girl Who Leapt Through Time." I don't have a possession of its English version (nor if I knew whether there's one or not), so these series' explanation would solely comes from my obviously lacking Japanese ability.

放課後の校舎は、静かで何かしら寒々しい。時々どこかの教室の扉の開け閉めされる音が誰もいない廊下の通路に響く。講堂のピアノで誰かがショパンのポロネーズを弾いていた。

"The school building after the school was out. Quiet, somewhat bleak. Sometimes, from some classroom somewhere, a sound of sliding door resonated into the empty corridor. Someone was playing Chopin's polonaise on the auditorium's piano.

＊放課後の校舎は、静かで何かしら寒々しい。

放課後・ほうかご "after school. Literally, set free, lesson, after"
校舎・こうしゃ "school building"
静か・しずか "quiet"
何かしら・なにかしら "somewhat"
寒々しい・さむざむしい "bleak"

Marked with は particle, the topic of this sentence is 放課後の校舎 "school building's after school period." What about this particular "school building" on its "after school period"? It was 静か "quiet," and 何かしら "somewhat," an adverb that modifies 寒々しい "bleak." Together, these components formed "quiet, and somewhat bleak."

Combined with the topic, the sentence becomes "A quiet, and somewhat bleak school building on its after school period."

Note on 静か. In the sentence, this word changes into its て form and as a rule for na-adjective as this word, its て form is given as 静かで.

＊時々どこかの教室の扉の開け閉めされる音が誰もいない廊下の通路に響く。

時々・ときどき "sometimes"
教室・きょうしつ "classroom"
扉・とびら "sliding door"
開け閉め・あけしめ "opening and closing"
音・おと "sound"
誰も・だれも "anyone"
廊下・ろうか "corridor"
通路・つうろ "pathway"
響く・ひびく "to resound" 

Even if on the outset, this sentence looks long and complicated, in reality, it was a relatively simple one. You just need to break it down properly. The subject of this sentence, marked with particle が is 時々どこかの教室の扉の開け閉めされる音. Or simply, 音 "sound" modified by the chains that precedes it.

The modifiers are, from the beginning, 時々 "sometime," どこか "somewhere" added with の particle, 教室 "classroom" and another の particle to indicate possessive, 扉 "sliding door" (contrast this with ドア "(western style) door") and yet another の particle, 開け閉め "opening and closing" and finally される, a passive form of する "to do." These modifiers, modified the "sound" to become "Sometimes, a sound of classroom's door somewhere, opening and closing."

So, what is this particular "sound" doing? 誰もいない廊下に通路に響く. Or, picking the most important (the only) verb, this "sound" is simply doing 響く "to reverberate; to resound; to echo." The words that precedes this 響く is simply adding extra modifiers to it. Let's take a look.

First of all, 誰もいない. A combination between 誰も "anyone" and いない "no one" to put an emphasis to "nobody, not a single soul." This "no one" becomes an attribute to the noun that follows it which is 廊下の通路 "corridor's pathway" which marked with a target particle に and thus becomes the target of the aforementioned verb 響く "reverberate."

Finally, the complete sentence becomes, "Sometimes, a sound of classroom's door somewhere, opening and closing, reverberating to the corridor's pathway that has no one in it." Or at least, that was the idea.

＊講堂のピアノで誰かがショパンのポロネーズを弾いていた。

講堂・こうどう "auditorium"
誰か・だれか "someone"
弾く・ひく "to play"

In Japanese language, ordering of sentence's components does not matter much as long as each of them marked correctly with a proper particle to define their respective role in the whole sentence.

This example, for instance has three main particles and a couple of の particles which I often considered as a part of phrase rather than independent particle especially if it takes a possessive role such as in this one. The three particles, in order, are as follows. で marks 講堂のピアノ "auditorium's piano" as an instrumentation, often translated in English as "by." Therefore the first order becomes "by auditorium's piano."

The next order, が marks 誰か "someone" as a subject. And the last particle in order, を marks ショパンのポロネーズ "Chopin's Polonaise" as a direct object. Finally, at the very last of this sentence, the verb acted upon this direct object 弾いた a past-form of 弾く "to play."

Thus, the sentence in its entirety becomes, "Someone was playing Chopin's Polonaise on auditorium's piano."

The order of this sentence could be different and yet it would still convey the same idea as long as there's a proper particle that marked each part in accordance to its role to the sentence. For example, this sentence could be rewritten as 誰かが講堂のピアノでショパンのポロネーズを弾いていた.