Music

[Cavernio]

There's alotta things that go into why people like music. If you've ever studied music theory, you'd know some of them. And before everyone rips me apart for this, saying "but I like music which doesn't do that", I'm not saying this is an end all and be all of what people like to hear. I think the best way to describe it is to describe what makes music different from other sounds.

First: beat. People like beats. The beat doesn't have to be thumped, it can be implied with a regular tempo and emphasis of .
Second: melody. What makes something a melody instead of random notes? Well, it follows the mode of the song. I guess a mode is best described as a set of notes or frequencies. Not all scales/modes have all the possible notes in them. You probably know of major and minor, but other ones exist like, umm, the one that you think about with traditional chinese music. When you stick to notes in your scale, you're more likely to get something that sounds pleasant. There's also other things involved, like outlining chords from the scales, following patterns, don't jump around too much, repetition etc.
3 chords. Your melody writing should already be implying chords anyways, so this really isn't its own thing. When looking at 2 or more notes/frequencies, there's consonance and dissonance. 3rd are consonant, so are 5ths. If you've got an instrument, play c and b. They don't sound good together. (dissonance) Now play c and g. They sound good. (consonance) There's actually physics behind this, and if you take the ratio of the frequencies (in hertz) of the 2 notes, one's with, umm, 'easy' fractions (1/2, or 3/4) sound good. Ones with ugly fractions, don't.
You also have to pay attention to WHERE the emphasis of a melody belongs. You want to place chord notes on the stronger emphasis of the beat.
4. timbre: This is one I don't know a whole lot about, and I really don't think its been looked at much in terms of classic music theory either. This is essentially the quality of the sound. Why a piano doesn't sound like an electric guitar, even if they're playing the same note. Some timbres have more 'color' to them. The more color, the closer to white noise (ie: no 1 note or frequency in it) it is.
Now, pretending you've done all that, you're going to have a pretty boring song if you never do syncopation (play around with the regular beat), always have chord notes in your melody, always have the right chord underlying the melody. What's interesting is that what is often found to be the most satisfying in a piece of music is when the 'rules' are broken, but then there's a resolution. Like when there's an ugly chord which magically turns into a nice one, by only moving 1 note of it down a semi-tone.
Definitely the fact that you even HEAR something more often makes that music that much more enjoyable, as a general rule.

Personally, (no outside knowledge about this), I think there's a drive to listen to something more and more noise-like and less music-like the more music we listen to. Also, catchy music is probably more music-like.