cap changes can cut bass, shunting to ground can cut highs - how to cut mids?

[amonte]

Sorry, this is probably a very basic question but it is something that I haven't fully grasped yet.  I always have trouble understanding how to cut certain frequencies.

If you're working with a simple signle transistor design, is there an easy way to do this? 

[Mike Burgundy]

Basically, a cap in series is a high-pass filter, a cap shunted to ground (or in a feedback loop) is a low-pass filter. A mid-scoop is a high-pass plus a low-pass, with their corner frequencies sufficiently away from each other. I've never tried to do this in a one-transistor design, and they will interact, but it might be worth a try to breadboard something. Say a 1.5KHz high-pass, a 250Hz low-pass, and try to combine the two. Don't think it will be great, though, but I'm sure someone will chip in.
With one dual opamp and a handful of parts you can make a gyrator-based parametric EQ (search the forum, there's some here). Low parts count, tunable, and adjustable boost and cut. Still low parts-count. Well, maybe that transistor comes in handy as a buffer - you should have that too
hih