ProggyMan

And phsychedelia, and pop...Alt Rock nevver struck as a truly viable genre. And it's obviously not pure rock. Funk-Rock is their actual genre.

Rainard Jalen

Alt Rock didn't? ROCK didn't. "Rock" as a general term has absolutely no distinguishing stylistic criteria. "Rock" doesn't tell you what instruments will be used, what vocal style, what time signature/beat, or anything else. Terms like Rock, Punk, Hip-Hop and Country have a lot more to do with cultural associations than firm stylistic grounds. You can say that the Chilis are not a prototypical rock band. But by association and cultural standing, they most definitely qualify as "rock".

ProggyMan

It's not good form to revive old arguements. Anyway, there are tons of things that are associated with rock(Musically I mean), such as penatonic scales, a strong back beat and prominent vocal melody. As to rock not indicating instruments used, almost every rock band ever has has drums, bass, guitar, and some other instrument, usually keyboard, mellotron, and synthesizers.

Rainard Jalen

The point is, those things could also be used to identify other "genres".

As has virtually every country band and funk band, ever.

It's really not possible to capture everything that the term "rock" is used to refer to in a simple, single definition. In fact it's used to refer to styles that are so different as to hold virtually nothing in common at all except for being music. You are right in saying that there may be certain qualities that are prototypically "rock", but the term itself has long branched out way beyond that.

If you were to compile all the different styles that are referred to in any possible context as being "rock" and look for one thing in common, the best you'd come up with are the sorts of audiences that the music attracts.