Just found this project... The hardware is different, but the philosophy is the same. This Psoc stuff is new to me, but looks really cool. I'll have to keep an eye out on ebay for cheap development boards...
I just want to point out that i'm fairly sure audio filters cannot be multiplexed, even if they are based on a dedicated IC.
I believe they can be multiplexed, however, the filter's amplitude, center frequency, and cutoff frequencies would need to be "retuned" for each band, during each cycle. Even if you had only 2 bands, it would be rather difficult, and probably more involved than simply making 8 (or 10) dedicated filters. (On a side note, this was the problem with early AM radios, before the invention of the superheterodyne, quality, "variable center" bandpass filters are very difficult to make). Im unfamiliar of the single chip bandpass filter linked, so I can't really comment directly on that. If "programming" the filters center and Q isn't difficult, the only problems I can see would be delay time.
To be fair, I'm just beginning to research this myself. However, switched capacitor filters seem to be designed specifically for variable-parameter use. The MAX260 I'm going to experiment with has a small up bus for communication. The frequency selection for all these devices seems to be the clock ratios you need to provide. The time required for the filter to stabilize between tunings should not be much of an issue because the sampling clocks are very fast, usually 100 or more times the center frequency. The level of difficulty is probably subject to perspective. When used in a ucontroller environment, there's really not much involved with sending the appropriate control signals. For me, the simplicity of a one chip circuit vs a whole board of discrete filters is a bonus. Not to mention the versatility I aluded to before of changing bands as I like on the fly. Obviously, this is not a solution for everyone, but it is a method I've not seen used much. I'm sure commercial devices like a stereo 10+ band hifi analyzer do not rely on 20+ stages of discrete filters.
