June 10, 2009 > TechKnow Talk: Making Music the Old-Fashioned Way
TechKnow Talk: Making Music the Old-Fashioned Way
Three hundred years ago, playwright William Congreve wrote the often misquoted, "Music has charms to soothe the savage breast; to soften rocks, or bend a knotted oak." While most of us would consider that excessive poetic license, we can agree that listening to music can be a pleasant and calming experience.
In Congreve's day, orchestral music was produced by four classes of instruments: brass, woodwind, string, and percussion. For the most part these instruments are still used today, fundamentally unchanged for hundreds of years. How do they create the pleasing noises we call music?
Like all sound, music is composed of acoustic waves. These are regions of alternating high and low pressure traveling through the air. These vibrate the ear drum of the listener; such vibrations are interpreted by the brain as sound.
The distance between each of these regions of compressed air is the wavelength. The number of waves reaching the ear each second is the frequency, which determines the tone or pitch perceived by the listener: the shorter the wavelength the higher the frequency and tone. The density of the compressed regions is the amplitude or volume of the tone. When many instruments are played simultaneously, the complex interactions among the acoustic waves provide the richly textured sounds of a band or orchestra.
Not surprisingly, brass instruments are typically constructed of brass or similar alloys plated with brass. The sound is produced by vibrations of the player's lips in a cupped mouthpiece. This vibration creates an acoustic wave within the horn. This wave resonates within the column of air inside the tubing. The wave exits the "bell," or flared end of the horn.
The musician can modify the tone only within the limitations of the length of the tubing. Only certain specific frequencies create "standing waves" in the horn, based on the length of tubing available and the wavelength of the sound produced by the player's lips. A trombone offers a long slide so the musician can change the length of tubing to support each desired frequency.
But most brass instruments, such as trumpets, French horns, and tubas, have valves for this purpose. When depressed, valves open additional lengths of tubing to increase the overall length of the horn, accommodating standing waves of lower frequencies, allowing the musician to produce intermediate tones. For example, a bugle is similar to a trumpet with no valves. With this fixed length, it produces only the specific tones compatible with its length, and not those in between.
Some brass instruments have a uniform tube diameter except for the flared bell; others are made with a gradually increasing or conical diameter. This difference in design alters the nature of the standing wave, affecting the quality or "warmth" of the tone. The tone produced by a French horn (conical bore), for example, is more mellow or "warm" than that from a trumpet (cylindrical bore), in part for this reason.
The woodwinds comprise another class of instruments. Flutes and similar instruments such as piccolos are played by blowing across an opening near one end. The frequency of the wave is determined by the length of the tube. Keys are provided at various points along the tube. When pressed they open or close holes, increasing or decreasing the effective length of the tube. As holes are opened further up the flute, closer to the mouthpiece, the frequency (tone) becomes higher.
Woodwinds such as the clarinet or saxophone use a reed. This is a thin piece of wood or "cane" similar to a very thin, short tongue depressor. As the player blows across it, the reed vibrates. Otherwise, the sound is produced in the same way as with a flute, by depressing keys to open or close holes along the instrument, modifying its effective length. Many reeds are now made of more durable plastic rather than the traditional wood.
Double reed instruments operate on the same principle, except they use two reeds joined at the edge, but allowed to vibrate independently. The result is an unmistakable, unique sound. Double-reed instruments include the oboe and bassoon.
Despite the name, not all woodwind instruments are made of wood. Most flutes and saxophones, for example, are metal. Some woodwinds are curved while others are straight. Though this may shape the quality of the tone to some degree, as with the brass instruments it is the overall length that is important to the resulting frequency, not how many bends there are along the way.
Stringed instruments use a very different mechanism to make music. A vibrating string compresses the air directly, through its back and forth motion. The tone is determined by the length of vibrating string and its tension. In most stringed instruments, the musician traps or "stops" the string with a finger along the neck, reducing its effective length, to play higher frequency tones.
An exception is the piano, in which a separate string is provided for each tone. The harp also has many strings, though not a sufficient number to produce all the requisite tones. While lengths remain unchanged, the harpist changes string tension to alter the vibrational characteristics and generate multiple tones from a single string.
Most stringed instruments are outfitted with a wood enclosure as a resonating chamber. The vibration of this enclosure "amplifies" the acoustic wave produced by the string. The musician can alter the quality of the tone in many ways, including by whether the string is bowed, plucked, or struck. Just as longer tube lengths support longer wavelengths (lower frequencies) in brass instruments, longer strings support lower frequencies as well. A tuba produces lower tones than a trumpet, and the long strings of a cello produce lower tones than a violin.
Percussion is perhaps the most varied family of instruments. There are dozens of different types of drums, ranging from the orchestral tympani and kettle drums, to the bass and snare foundational to marching bands, to conga and bongo drums.
Most of these operate on a similar principle. The vibrating medium is a membrane or "head" stretched tightly across the top (and in many cases the bottom) of the drum. This is struck with a blunt, often padded, stick to induce the vibration. The resulting acoustic wave pushes the opposing head outward initially then resonates back and forth within the metal or wooden body of the drum. Some drums are open on the bottom, but shaped in such a way as to contain the pulsing air, allowing only a portion to escape with each pulse.
The tension with which the head is tightened determines its frequency. Some drums (such as timpani) may be tuned to very specific frequencies, while others are used solely to provide rhythm, without regard for tone. Drum heads were traditionally made of animal skin; today most are plastic.
Other percussion instruments include cymbals, gongs, chimes, xylophones, blocks, tambourines, triangles, and a host of others - even cowbells are sometimes used. In addition to providing rhythm and tempo, percussion instruments can add a great deal to the mood and drama of a musical composition.
In recent decades, electronic amplification and modification has become common, especially for popular music. However, with a few exceptions such as synthesizers, live music is produced acoustically using one of the techniques described above, little changed for centuries.
Finally, much has been made of the materials, designs, and craftspeople used in the manufacture of fine instruments, especially the string family. This is indeed a consideration at the very highest level of musicianship. However, these factors are of less importance than may be imagined. Most of us would have difficulty distinguishing between the sounds of a $1000 violin and an exquisite violin worth $100,000. Stated another way, a good musician playing a great instrument is no match for a great musician playing a good instrument.