The Schubert link demonstrates one of the real bugbears of classical music which is streamed or ripped using the usual online metadata database: "Death and the Maiden" is #46–49, presumably because it was tracks 46 to 49 in the boxed set. In reality, it is a 30 minute piece in 4 parts which is normally performed on its own.

You wouldn't normally listen to just one part ("movement") and rarely to more than a couple of pieces at a time. Classical pieces are usually numbered ("opus", abbreviated "Op.", which is Latin for "work"). Schubert is one of those composers who didn't number them himself. He died young of syphilis and left his manuscripts in a disorganised mess. They were sorted through by a guy called Deutsch, hence the numbers here are "Deutsch" numbers. Here, "Death and the Maiden" is D. 810.

The Italian after the Roman numerals for the movements are speed markings ("allegro" = "fast"), and this piece shows a typical progression: fast, slow, playful/fast, faster. They should be listened to in order, one after the other. The idea is that the music takes you through a sequence of moods, like courses in a dinner.