Two of the five families of musical instruments suffer from problems with tension. Putting things at the most basic level with the other families, for wind instruments, all one needs is something hollow with at least one orifice into which to blow; for idiophones, something solid that is rigid enough to clang when struck; and for electrophones, a power source. But both skin instruments and string instruments need tension. When they are slack, their skins or strings can never produce a useful sound. Both need some way to tighten them and moreover to keep them at a steady and unvarying tension, because if the tension changes, so does the pitch, and they go out of tune.
Three things control their tuning: their size (diameter for drums, length for strings), their mass (the thickness, weight, and density of the skin or strings, all of which are components of mass), and the tension of skin or string (their flexibility is a major factor for tone quality but not for pitch). Size is mainly controlled by the construction of the instrument. Only with those string instruments where one can shorten the sounding length of a string to raise its pitch, as one does on a guitar or violin, is it practicable to change the effective size in performance. The mass is controlled in production; it cannot be varied in performance.
Fortunately, there are many ways to control the tension, for all strings and drums do need to be tuned. Even the drums without a nominal fixed pitch need to be “tuned” to the optimum playing tension, and the only way left to do this is by altering the tension. The first problem is how to do this, and the second— and more serious—is how to keep it done. Tuning devices that slip mean constant troubles with keeping in tune. For string instruments, the invention of the tuning peg, fitting tightly into a hole and held by friction, is comparatively recent, probably somewhere in the early years AD. The machine tuning head, a worm and cog such as we use now on guitars, is even more recent and was first devised for the double bass in the early eighteenth century; it was applied to late citterns such as English guittars in the second half of that century and to Spanish and Portuguese guitars even later. The fine-tuner, used now on the metal strings of the violin family, was probably an early-twentieth-century invention, or perhaps late nineteenth.
Until plastic drumheads were invented in the midtwentieth century, nobody had ever found a way to keep drum-skins taut in damp weather, although the use of rope-tensioning on our military drums was a brave attempt. The theory was that as the drum-skin stretched with the increase in humidity, the rope would shrink, the one balancing the other, but it never worked really well. Rope or thong tensioning is one of the easiest ways to tension a drum-skin, but we shall meet many others, and today in our culture, and spreading elsewhere, it has mainly been replaced by rods screwing into brackets.
The next problem is how to support the tension needed for any pitch. Few materials are really rigid—almost anything will bend in time, given enough tension or weight on it. When it bends, it changes its length, becoming shorter as the two ends move nearer together. Once the length or shape changes, so does the pitch, and the instrument is out of tune. If the instrument was not straight to start with, but curved, it is all the more likely to bend further under tension. If the instrument is made of more than one piece, the area of the joint between those pieces is a natural point of weakness where tension will break the instrument apart. In later chapters, we shall see how troubles with tension have been dealt with on string instruments. Here our concern is with the drums.
Drums: Ancient Instruments and Their Evolving Function
