Why doesn't a digital recording of a piece of music contain all of the sound available?

Answer 1

The full answer to that would be fairly long and complicated, but this is the basics:

Sound - unless it goes entirely quiet - is a continuous, unbroken event. But digital recording, by definition, is a long series of samples. A long series of small, separate moments.

Basically it's taking a slice or a snapshot of what happens right now, waiting a tiny moment, then taking another, and another, and another.

If the samples are small enough, and the pauses between samples are small enough, when the sound is played back, you can't hear that it consists of separate pieces stringed together.

Pretty much like video is a sequence of stills stringed together and replayed at a rate high enough to make the images blend together.

Then there is compression.

Usually, from the perspective of electronics, not much happens from one sample to another. And saving all the information - most of which just like the one that went before - just seems like such a waste of memory space.

So people have come up with clever schemes where they record the differences instead, and not all the original content. It saves plenty of memory space, but some of the music gets lost too,

Compression format are mp3, Wav and similar.