I was talking to my girlfriend's brother about 30 Seconds to Mars, and, well, this conversation took place...
Me: It irritates me that they call themselves prog.
Him: They do? Wow. That's lame, they're emo!
Me: ...No they're not.
Him: Dude, they totally are! They write all kinds of depressing stuff.
Me: And? Bands from every genre do that, that doesn't mean anything.
Him: Yeah, but it's ALL they do.
Me: And? Lyrics don't define a genre. Sound, technique, and song structure among other factors is what shapes a genre.
Him: Dude, what if Led Zeppelin wrote a song about cutting their wrists?
Me: If "Black Dog" was about cutting your wrists, that would be a rock song about cutting your wrists.
Him: I don't know, man.
Me: But I do. Emo is NOT defined by lyrics at all. People lump in bands like 30StM and Coheed with emo simply because a lot of scene assholse like it, and no one knows what "emo" actually is.
He stopped arguing with me and I didn't want to pound the idea into his head.
Now, I know that he's obviously wrong, that's not really what my question is.
I have a faint idea as to what 3rd wave of emo entails and how it sounds, but I'm a lot better at picking out what ISN'T emo versus what is.
So what precisely is it that defines emo as a genre so I can actually (hopefully) try to explain to my girlfriend's brother why 30 Seconds to Mars isn't emo just because Rock Band put them into that genre?