> (although it does operate rather on a continuum basis)

Actually, consonants are pretty discrete. You can move your tongue further and further back and it is still perceived as the same fricative (for example), but move it just a bit further back and the quality of the sound changes completely to another fricative.

Vocals, on the other hand, are continuous, so that miniscule changes in your jaw-tongue configuration makes it sound differently.

That's why you usually recognize non-native speakers by their vowels. It takes many years to get vowels right.