A Couple Little Things I'm Wondering About

Sorry, but speed of electricity in the wire is dielectric dependent and is far from the speed of light (around 0.6 of it).  In practical terms it is approx. 5ns/m in typical insulated wire and 3.33ns/m in the vacuum.
Since dielectric affects the speed of electricity it also affects capacitance, dielectric absorption etc.   As for audibility - I don't know, but don't know enough to call it ludicrous.  

Really ? If it was audible then the only way you wouldn’t have a weird staccato effect in your music is if the wire floated. Either have the cable float or lay on something having little holders every so many feet or inches would really mess up the music, you know if insulation touching something was audible.

Gimme That Old Time Religion, Gimme That old Time Religion...... (ad nauseam)      They’re still trying to evangelically compel those electrons ("charge carriers"), through a conductor (HALLELUJAH!).        Anyone interested in today’s science, can read the, ’Electric Drift’ section, of the aforementioned wiki-science article.               Particularly, the last sentence (since we’re talking AC).        Note that these things are measurable, established and documented.        When one of these faith-in-outdated-science, religious fanatics can prove (via any 20th Century Science/Physics) that the above factors have no bearing on what we’re hearing, I’ll accept their version of salvation.      Is there a purgatory, for repentant doubters, in the Naysayer Doctrine?

The drift velocity of electrons in copper wire is around 1 inch per minute!
Current occurs immediately almost at the speed of light.  Kijank is right that the dielectric affects the speed and field strength. But also important is the presence and distance to the return. If close the fields cancel out.

Staccato effect?  Sure, for people who can hear tiny change in few nanoseconds between supports  (hundreds of MHz). 
Let's assume that somebody can hear the difference.  To me it doesn't matter if this difference is real or it is only a placebo effect.  Outcome is the same.