[sdiy] stupid cap question

[Antti Pitkämäki]

Hi!

This isn't exactly on topic since it's a question about basic electronics 
and not synth DIY, but I hope you guys don't mind I ask this here.

So: Lately I've really tried to learn about electronics, so I could learn 
not only to build stuff but also to understand how they work. I understand 
all the basic stuff, like Ohm's law, Kirchoff stuff, and I also understand 
some stuff about transistors and tubes, but there's one very basic thing 
that I don't exactly understand why it happens. It's about capacitors. I 
understand that they block direct current because of the very high 
resistance between the plates (or block after being fully charged!). I also 
understand what happens when u put them in series, parallel etc. I also 
understand why there can be accent current in a circuit with a capacitor, if 
the other plate is connected to AC source and the other one to ground -  the 
cap is consantly charged and discharged (or I can understand why it happens 
on the plate and part of the circuit that is connected to the AC source). 
But why does accent voltage, well I mean signal, actually pass the 
capacitor? What happens there? All the books I've read simply say that it 
happens but they don't say why. There are all the theories about coils and 
transistors etc., and I understand them, but why, oh why does AC, or maybe 
it would be more correct to ask, why does accent voltage, pass a capacitor 
since no electrons can actually go trough it? What's the theory behind this?

I know all I would really need to know is simply that accent voltage passes 
a cap, but I'm one of those people who want to know more :) I hope my 
question made any sence!

Please help me so I can sleep ;)
Thanks in advance,
Antti Pitkämäki