It's a tough question.
A while back a guy I know made me think when he suggested there are different sorts of music. Not as in rock/pop/rap, but as Art/Entertainment/Folk.
You have music made as an artistic statement, which doesn't necessarily mean it has to be weird/experimental in sound, it just has to have something about it beyond mindless entertainment. You have entertainment which I suppose novelty music would fall under, and pop music, and your typical cookie cutter metalcore bands. And then folk, which doesn't so much concern itself with how it sounds, more of the stories it tells, and the tradition being passed on.
Of course those 3 aren't necessarily definite, I've heard people suggest other categories, such as experimental, and some have different definitions for them, but for me, these seem to make at least some sense.
For music as art, I like it to have a good atmosphere about it, I like it to feel as if simple element's have come together in order to make something that feels greater than the sum of it's parts. I don't think good lyrics are essential. I think it can be a bonus, but a lot of the time I don't have a clue what's being sung, but it doesn't matter, as sometimes it's more adding a texture to the music, or a feeling to it. As Robert Smith of the Cure once said, sometimes understanding lyrics isn't half as important as they way they are sung. As if they are sung right, you convey a feeling, and even people who don't understand your language can feel what the song is about. But for me someone could be singing about the glory of the third reich and as longs as the music was good, I would let the subject slip. Which I suppose leads to my next point, and sort of ties in with the previous point, I place actual musical content above the lyrics. They could be the greatest lyrics ever written, but if the song around it is no good, then they may aswel be poetry for all I care.
Also it doesn't necessarily need to be instantly acessable. Sometimes the beuty is in absorbing an album over multiple plays, and finding little intricacies over time, and growing to appreciate it.
On top of that, more often than not, I prefer an album to be like a complete work. Not just a bunch of random songs thrown together, I like it feel like something that was meant to be, as if those songs where recorder for a purpose and where supposed to go on that album in that order.
I like it to feel as if it was an album of music written with intent, rather than a few guys jamming a few chords and writing it on a whim.
Then there's music for entertainment. For this I feel there has to be instantly acessable. I think it needs to have a good energy about it. and it needs to be catchy. I don't think there needs to have a purpose about it, it could have been written for the sake of being written, as long as it gives you a temporary fix of what it is your looking for in your music at the time. But again, for me lyrics aren't of much importence, though I do like a chorus to be catchy if it's to have one.
I suppose there's a cross over between the two, stuff that you use for entertainment, but does have some sort of artistic value.
And then folk music. For me I like it to tell tales or real things, or real folklore/myths. And I'm particularly fond of local folk songs. Though really with folk I'm slightly less picky. Though nice guitar playing, and traditional instruments are a bonus.
But again there's crossover with folk and entertainment and art.
However they are all quite vague reasons. And don't really say how I define good music, more what I like about music, which I suppose you could argue is what I think is good. But I don't think you can Define good music as such. For a start you have to ask what is good music? Is there anything objective about music that is good regarless, that even if humans didn't exist would be good? Even within your self. I couldn't say I liked all music with a choir for example, as I might not, there's always going to be subjectivity, and even if there was objectiveness, it wouldn't necessarily explain why something is good, more what it is you like about it. But I think I'm getting carried away on a train of thought and sort of going of on a tangent here.
At the end of the day, Define means to give meaning or definition to something, so how I would I define good music? I suppose the only satisfactory answer would be music that I think is good.
