Here is a Flex UI component I've been writing. Click the image to play with what I have made so far.
You can change a variety of properties. The dial and mark are runtime skinnable by setting its "dialBackgroundSkin" or "dialMarkSkin" property to a url with an image.
Knobs and dials just look cool...I don't know anything about audio editing but I like the site of a sound studio. This is the "Reason" I decided to make a knob component.