In music, a bow is moved across some part of a musical instrument, causing vibration which the instrument emits as sound. The vast majority of bows are used with string instruments, although some bows are used with musical saws and other bowed idiophones.
A bow consists of a carefully chosen stick (usually wood) with some other material stretched between its ends. The type of bow used to play instruments of the violin family has many hairs stretched between its ends, but bows used in other cultures often stretch a single piece of string between the ends of the wood.
Fine modern bows used to play string instruments of the violin family (the violin, viola, cello and double bass) are usually made of pernambuco wood from Brazil and are strung with horsehair. When choosing wood to make bows, a violin or a bow maker must choose sound quality above all. A common practice is to reserve the best and most beautiful wood for a maker's most expensive work. Some bows are made nowadays from synthetic materials, such as a carbon fiber epoxy composite, or fiberglass. Carbon fiber bows have become very popular, and some of the better carbon fiber bows are now comparable to the finer pernambuco sticks. Lower quality bows can also be made of synthetic materials and less suitable types of wood.
For the frog (which holds and adjusts the near end of the horsehair), ebony is most often used, but other materials, often decorative, are used as well; these include ivory and tortoiseshell. Near the frog is the grip, which is made of a wire, silk, or "whalebone" wrap and a thumb cushion made of leather or snakeskin. The tip plate of the bow may be made of bone, ivory, mammoth ivory, or metal, such as silver.
A bow maker or archetier typically uses between 180 and 200 hairs from the tail of a horse for a violin bow. Bows for other members of the violin family typically have a wider ribbon, using more hairs. White hair generally produces a smoother sound and black hair (used mainly for double bass bows) is coarser, producing a rougher sound. Lower quality (inexpensive) bows often use nylon or synthetic hair. Rosin, a hard, sticky substance made from resin (sometimes mixed with wax), is regularly applied to the bow hair to increase friction.
In making a bow, the greater part of the woodworking is done on a straight stick. According to James McKean (reference below), "the bow maker graduates the stick in precise gradations so that it is evenly flexible throughout." These gradations were calculated by François Tourte, discussed below.
In order to shape the curve or "camber" of the bow stick, the maker carefully heats the stick in an alcohol flame, a few inches at a time, bending the heated stick gradually to the proper shape. A metal or wooden template is used to get the exact model's curve and shape while heating.
The art of making wooden bows has changed little since the 19th century; most modern composite sticks roughly resemble the Tourte design, although the Incredibow marks a serious departure from it, having a "straight" stick cambered only by the fixed tension of the synthetic hair.
In modern practice, the bow is almost always held in the right hand while the left is used for fingering. When the player pulls the bow across the strings (such that the frog moves away from the instrument), it is called a downbow; pushing the bow so the frog moves toward the instrument is an upbow (the directions "down" and "up" are literally descriptive for violins and violas, and are employed in analogous fashion for the cello and double bass). Harnoncourt (1988) noted that the symbols for down-bow and up-bow are likely derived from early notation of "n" and "v" respectively, standing for nobile and vile (noble and ignoble, roughly), as the down-bow is usually utilized for the strong (more noble) beats.
Generally, the downbow stroke is used for the strong musical beats, the upbow for weak beats. However, in the viola da gamba, it is the reverse; thus violinists, violists, and cellists look like they are "pulling" on the strong beats when they play, whereas gamba players look like they are "stabbing" on the strong beats. The difference almost certainly results from the different ways in which the bow is held in these instrument families: violin/viola/cello players hold the wood part of the bow closer to the palm, whereas gamba players use the opposite orientation, with the horsehair closer. The orientation appropriate to each instrument family permits the stronger wrist muscles (flexors) to reinforce the strong beat.
String players control their tone quality by touching the bow to the strings at varying distances from the bridge, emphasizing the higher harmonics by playing sul ponticello "on the bridge," or reducing them, and emphasizing the fundamental frequency by playing sul tasto "on the fingerboard".
Infrequently, composers ask the player to use the bow by touching the strings with the wood rather than the hair; this is known by the Italian phrase col legno, "with the wood". Col arco, "with the bow", is the indication to use the bow hair to create the sound in the normal way.
The question of when and where the bow was invented is of interest because the bow made possible several of the most important instruments in music today. Authorities give different answers to this question, and this article will give only the predominant opinion.
Scholars are agreed that stringed instruments as a category existed long before the bow. There was a long period—possibly thousands of years—in which all stringed instruments were plucked.
In fact, it is likely that bowed instruments are not much more than a thousand years old. Eric Halfpenny, writing in the 1988 Encyclopaedia Britannica, says "bowing can be traced as far back as the Islamic civilization of the 10th century ... it seems likely that the principle of bowing originated among the nomadic horse riding cultures of Central Asia, whence it spread quickly through Islam and the East, so that by 1000 it had almost simultaneously reached China, Java, North Africa, the Near East and Balkans, and Europe." Halfpenny notes that in many Eurasian languages the word for "bridge" etymologically means "horse," and that the Chinese regarded their own bowed instruments (huqin) as having originated with the "barbarians" of Central Asia.
The Central Asian theory is endorsed by Werner Bachmann, writing in the New Grove. Bachmann notes evidence from a tenth century Central Asian wall painting for bowed instruments in what is now the city of Kurbanshaid in Tajikistan.
Circumstantial evidence also supports the Central Asian theory. All the elements that were necessary for the invention of the bow were probably present among the Central Asian horse riding peoples at the same time:
From all this it is tempting to imagine the invention of the bow: some Mongol warrior, having just used rosin on his equipment, idly stroked his harp or lyre with a rosin-dusted finger and produced a brief continuous sound, which caused him to have an inspiration; whereupon he seized his bow, restrung it with horsehair, and so on. Obviously, the degree to which this fantasy is true will never be known.
However the bow was invented, it soon spread very widely. The Central Asian horse peoples occupied a territory that included the Silk Road, along which goods and innovations were transported rapidly for thousands of miles (including, via India, by sea to Java). This would account for the near-simultaneous appearance of the musical bow in the many locations cited by Halfpenny.
The kind of bow in use today was brought into its modern form largely by the bow-maker François Tourte in 19th century France. Pernambuco wood which was imported into France to make textile dye, was found by the early French bow masters to have just the right combination of strength, resiliency, weight, and beauty. According to James McKean (reference below), Tourte's bows, "like the instruments of Stradivari, as still considered to be without equal."
Slightly different bows, varying in weight and length, are used for the violin, viola, cello, and double bass.
These are generally variations on the same basic design. However, the bow used for the double bass comes in two distinct forms. The "French" or "overhand" bow is similar in shape and implementation to the bow used on the other members of the orchestral string instrument family, while the "German" or "Butler" bow is broader and shorter, and held with the right hand grasping the frog in a loose fist. The German bow is the older of the two designs. The French bow, often chosen by soloists due to its greater maneuverability, was not widely popular until its adoption by 19th-century virtuoso Giovanni Bottesini. Both bows are used by modern players, and the choice between the two is a matter of personal preference.
Bows must be periodically rehaired, an operation usually performed by professionals rather than by the instrument owner. Rehairing is done when too many of the hairs are broken, or the hair is dirty, or has lost its friction. Sometimes changing the whole bow can be easier and cheaper than rehairing the old bow, especially with small fractional sized bows.
One way to prolong the useful service life of the hair is to clean it with shampoo or alcohol. Alcohol can damage the finish of the stick if care is not taken to protect it. Contamination of the horsehair with oil, grease, wax, or soap will make it lose its friction, leading to an uneven sound, or no sound at all.
Bows sometimes lose their correct camber (see above), and are recambered using the same heating method as is used in the original manufacture.
Lastly, the grip or winding of the bow must occasionally be replaced to maintain a good grip and protect the wood.
These repairs are best left to professionals, as the head of the bow is extremely fragile, and a poor rehair, or a broken ivory plate on the tip can lead to ruining the bow.