The equivalent single reed has a tongue carefully cut out of the side of the straw near the top, with the end closed by a natural node or an artificial stopper, and so one would think it to be much more complex to devise and less likely to have occurred initially by accidental discovery. And yet the simple single reeds, often called “folk clarinets,” are far more common in the world today than any simple double reeds.
The answer may lie far back in time. When both were grass or straw, and thus ephemeral since both are easily broken or so saturated by being held in the mouth that they will no longer spring open against the player’s breath, perhaps the double was the more common. Today, when the more efficient hard reed and cane is used, the single reed is quite easily made, whereas the double needs careful scraping unless, in the parts of the world where such plants grow, it can be made from a tube of a different, softer type of reed or from materials such as palm leaf.
The double reed has a pair of surfaces, either thin blades of cane, as with the oboe and bassoon, or a flattened plant stem or layers of palm or other leaf, as with many exotic instruments, that beat concussively against each other when blown. The single reed has a single blade of cane or other material tied to a mouthpiece, as with the clarinet and saxophone, or a blade cut from the surface of the mouthpiece but still attached at one end, as with many other exotic instruments, that beats percussively against the mouthpiece when blown. Both are so constructed that they lie slightly open and are forced to close, beating against each other or the mouthpiece, by the player’s breath or, in the case of organs and bagpipes, by the air from a bellows or bag
There is a third type of reed, the “free reed,” so called because it does not beat against anything but swings freely to and fro through a closely fitting slot. Its behavior and use are sufficiently different from the other two that we shall devote a separate section to it. A fourth type, a dilating reed that normally lies closed but is forced open by the air, is fairly rare when made from straws or other plants, but is used worldwide in the form of a player’s lips. Made of straw or plant-stem, it seems to exist only as a reed whistle, rather than driving a musical instrument. The player’s lips are sufficiently different from other reeds that they are better dealt with as “brass instruments,” a useful common term in our culture even though many other materials besides brass are used.
Irrespective of the type of reed used, there is a further distinction, discussed in more detail in the afterword, between those reed instruments with a cylindrical bore (the inside of the tube) and those whose bore widens from top to bottom. The latter are easier to play over a wide compass because, when blown harder, the pitch jumps up (or overblows) an octave and the player can use the same, or at least similar, fingerings to produce the same pitch names an octave higher than before. The fingering for a C, for example, or any other note is much the same in each octave. However, all the archaeological or iconographic evidence that we have tells us that reed instruments of this expanding shape are much later in the history of the development of instruments, presumably because such a bore is more difficult to make than a plain cylinder.
The reed instruments with cylindrical bore (it is necessary to repeat “reed instruments” because flutes behave quite differently) are difficult to overblow at all, unless helped with the speaker key found on our instruments, and when they do sound in a higher register, the pitch is a twelfth—an octave and a fifth—above the original range; thus the same note names in the higher register have very different fingerings from those in the lower register. The fingering for a C in the lower register would, with the addition of a speaker hole or key, produce a G in the upper register. On instruments without keywork, there is often a gap in the compass between the top of the fundamental register and the bottom of the overblown register, simply for lack of sufficient fingers to control enough holes to cover the whole compass. The difference between the fingering of the two bore shapes is well known to those who play both saxophone (which widens in bore) and clarinet (which is cylindrical).