A preamp is a good idea for analogue switches (4066, or 4051/2/3) since they have relatively high on resistance. But using them for audio there are a couple of issues. Firstly, the signal being switched has a limitation of the supply rails. The CD4053 series has a 'VEE' pin, which can go as low as -5V. This is to allow one to route analogue signals that go above and below ground (= audio). The CD4066 doesn't have this facility (as far as I know) so if powered by 9v, the input signal can only be between 0v and 9v.
However, ronv has cleverly added bias resistors to the inputs. The input capacitor blocks any DC offset (so your input signal is centered around 0v, ground) and the two 47k resistors shift this so it is centred at half the supply voltage, 4.5V. Meaning your analogue signal will start to clip at around 4.4V - but most line audio is 1V peak to peak, and guitar signals generally stay below 3v p-p. The outputs are coupled with capacitors to remove this 4.5 offset, returning the signals to 0v centered. The one caveat with these bias resistors is the input impedance. with 47K resistors thats around 23k input impedance. Fine if it is being fed by a buffer, or 'audio out', but if it is straight from a guitar, you'll want a buffer on the input too, one with high impedance.
The second issue with logic analogue switches is the off resistance. As I'm sure you're planning on amplifying the outputs, any 'bleed' through of the signal could well be heard after amplification. Although the off resistance is measured in megaohms, and ron's schematic has bias resistors on the output, there still may be some bleed through in the output from unselected inputs. A quick way to sort this is to shunt the unselected inputs to ground with another 4066, or mosfets. This makes sure NO signal goes though the switch and couples to the output when it isnt' selected. It also prevents 'crosstalk' between analogues switches in the same package.
There are actually quite a few app notes about this subject, because, as you noticed, maxim like to plug their line of awesome analogue switches, and point out the flaws in existing designs. Whilst they are obviously promoting their product, they make some excellent points. - Doesn't mean to say we have to use maxims chips though!
All in all, using the analogue switches can be very useful, but certain precautions must be made for a 'clean' transparent routing of audio, which means a few extra circuits before and after the switches - especially for pre-processed signals, where any noise/distortion/crosstalk is bound to be amplified by later processes in the audio chain.
If you're a guitar pedal fan, you can check out schematics for the boss series of pedals. Their bypass switching uses JFET's, same principle as your idea, just with only two possible channels, works on 9v, is low power, and as its designed for 'guitar input', does very well to keep signals 'clean'.
I have had similar projects in the past, and have collected a fair bit of info on it (for analogue multieffects). So, even though I tihnk ronv has done a smashing job with that schem, simple but effective, if you have more questions, I'm all ears
Blueteeth