I think a solid understanding of all of the principles involvled in the Voyager would help you navigate. Although I imagine that's not everyones cup of tea.
First of all, I should mention that I'm no Moog expert, I'm more of a Moog groupie ( I don't own a moog) but I'll start the Filter discussion and hopefully others will jump in and add to it.
Filters do pretty much what you might expect any kind of filter to do- your coffee filter for example, it lets some things through and stops other things from getting through. (electronics can be a bit more complicated than that but let's ignore resonance for now.) But what are the “things” and why would you want to stop them?
To understand what the “things” are in the case of your voyager it helps to know a bit about how you can take something complicated, like the sound of a musical instrument- a plucked guitar string for example and break it up into more simple components which when all added up together give you the original sound.
To make a long story short (we can make it longer if you want) a complicated sound like a guitar string pluck can be broken down into it's fundamental frequency, That is, the lowest frequency of the note being played and integer (2, 3, 4, 5 etc) multiples of that fundamental frequency. So for a low E guitar note which has a fundamental frequency of about 82 cycles/second, there's a frequency component of 82, and a harmonic of 2 X 82 or 164 cycles/second, and another harmonic of 3 X 82 or 246, and 4 X .... etc. you get the idea. For an acoustic guitar, it takes about 80 of these harmonics to give a pretty realistic sound of a guitar. These harmonics, and how they change over time, that is, how they “attack” or start and how they decay (acoustic guitars don't really have sustain) are a way of understanding the details of the original complicated sound.
These frequencies that I'm talking about can be looked at as basic building blocks of complicated sounds. They are sine waves- simple oscillations. By themselves they're not very musically interesting but when you combine them you can make all kinds of interesting sounds.
Now with analog electronics, especially back in the day, it's not so easy to make a complicated sound by starting with a lot of simple oscillations and adding them all together. It was and is much easier to start by making something which electronic components are more suited to make which also has a rich assortment of frequencies already in it.
One example of something easy to make that contains rich harmonics is a square wave. Here's a link that explains it. You may just want to look at the animation which shows how a pure sine wave becomes a square wave by adding more harmonics.
http://en.wikipedia.org/wiki/Square_wave
A square wave contains the fundamental frequency and odd harmonics. The more square the wave, the more odd harmonics you get.
A triangle wave contains odd harmonics too but the harmonics are not as strong as the fundamental. You can read about it here
http://www.thedawstudio.com/Tips/Soundwaves.html
So, getting back to your Voyager. You start by making a fairly complicated sound that has a lot of harmonic content. But the content is very regular, and that regularity limits how interesting it is. Then the filter takes away some of the regularity, that is, it removes some of the harmonics, taking away some of the harmonics in different ways provides a lot of variety of sounds and also makes individual sounds more interesting.
Getting back to the acoustic guitar for a moment. As I mentioned, the low E note needs about 80 harmonics to sound like an acoustic guitar. But it needs more than that. To sound like a guitar the high frequency harmonics have to decay faster than the low frequency harmonics. On a guitar, the way strings and wood behave makes that happen. You can get a similar effect on your Voyager, by sweeping the filter so that it starts by filtering the high frequencies first and then over time filters lower and lower frequencies. Of course, with the Voyager, you can get other effects too.
I'll stop here. I've introduced a lot of the basic concepts that you need to be familiar with if you want to really understand what's going on when you twiddle the knobs. Ask questions about any of this that needs clarification or ask a question that takes this to a deeper level. I'm sure someone will correct any errors I made and have other perspectives too.
