....is a bit too huge of a question for me to tackle but briefly*
But a lot of what happens in popular culture is relatively new or contextually new – it might be the drifting into (or conscious borrowing of) innovations that developed elsewhere (jazz, avant-classical etc) or from non-Western traditions. There are artists who do a mixture of things – some that are absolutely new (Beatles with “Tomorrow Never Knows” etc) and others that are contextually new (the kind of expressivity in “Eleanor Rigby” had never been heard in pop music before, I don’t think – although clearly in the novel or film that kind of mood had been broached before).
Or a more recent example – there was a phase in hip hop and R&B in the early 2000s, where you heard all these sounds and riffs from techno and house – it was very exciting (Timbaland et al) but at the same it was ground already broken in the early 90s in Europe. But in the context of rap it was a new thing and very exciting to hear on MTV / BET / the radio.
In terms of how innovation makes itself felt as such, I think there is no better analysis than Fredric Jameson’s in A Singular Modernity, particularly with this passage that I’ve quoted before, which captures the paradox of how we can listen to an old piece of modernist art or music or whatever, that ought to be stale and familiar, but somehow we can still feel its future-shock:
"the older technique or content must somehow subsist within the work as what is cancelled or overwritten, modified, inverted or negated, in order for us to feel the force, in the present, of what is alleged to have once been an innovation..... "The act of restructuration is seized and arrested as in some filmic freeze-frame" [and as a result the modernist work] "encapsulates and eternalizes the process as a whole."
That implies that innovation is always a move within and against an established tradition... I don’t think that is actually case – I think there are moments of absolute innovation (musique concrete, early electronics etc). But those are few and far between and you can’t count on a steady supply. So more often it’s a case of the push to make-it-new occurring within and against the old - e.g what Hendrix did with the electric guitar and blues, or what house did with disco, hip hop did with funk, etc, or jungle even more so with funk and reggae, or postpunk with its various sources.
Another thing to consider is that innovation can also be linked up to more regressive (politically or emotionally or simply in terms of narrative structure) elements. So - by far the most cutting-edge things going on with film on a technical level (effects, CGI, editing, sound, high def etc) occur in the most pulpy, lowbrow, and often reactionary or just simply juvenile areas of cinema: thrillers, action, superhero, kids cartoons etc. Likewise you can have radical sonic things or techniques going on within genres that are otherwise very traditional in their musical structures and their emotion affect or mode of usage. The engineering etc in a Top 40 hit is cutting edge, but everything else in it might be fairly conservative.
I don’t think the future-shock effect is really relative to how much music history you know... because what we’re talking about is musical events that are not reducible to references or influences... it’s a more-than-the-sum effect... not addition but multiplication
I suppose the super knowledgeable might be more likely to hear the older elements (the residual, traditional stuff that is being reworked or cancelled)... they might also happen to know of obscure precedents that preempt the supposedly new... but when something really truly new happens, the knowledgeable elder and the ignorant neophyte are in the same place really - dumbfounded.
Futureshocked.
^^^^^^^^^^^^^^
* "briefly" - famous last words! Well no one ever accused me of being a man of few etc etc
