Bore
From Oddwinds
Wind instruments usually are regarded as having either a cylindrical bore or a conical bore. In reality the bore is almost never purely cylindrical or purely conical, but one or the other predominates.
The acoustical properties of the instrument depend in part on the type of bore, as well as whether the bore is (effectively) stopped (closed) or open at one end. The fundamental tone of a conical bore instrument, or an open cylindrical bore instrument, has a wavelength approximately twice the length of the instrument, while that of a stopped cylindrical bore instrument has a wavelength about four times the length of the instrument. So a clarinet (stopped cylindrical bore) can reach a note an octave lower than an oboe (stopped conical bore) of the same length.
Furthermore, a conical or open cylindrical instrument overblows at the octave -- the second register begins twelve half steps above the first. A stopped cylindrical instrument overblows at the twelfth -- the second register starts nineteen notes above the first. This means stopped cylindrical instruments tend to be able to cover a wider range than the others, but it also means they need more holes and keywork, and more fingering complications, to handle the larger number of notes in the bottom register.
