Mind you, innovation can be innovation for the time as well. I'd just like to point that out. Mozart was innovative, and he is long dead.
Get my drift?
Edit: and furthermore, innovation is what it is, I'm more interested in styles that truly bucked the system at some point. Things that make people say 'that isn't music!' I'm just looking for the elements, they could be modern emulation, or in a work that is not by the original pioneer of that element. So long as it was at some point something that made some people go 'WTF, you aren't supposed to do that!'
I suppose old rock from the 50's and many other things technically would count, but I'm looking for exceptional and notable elements. Like using electric guitar for the first time is innovative, but it isn't far fetched either.