Hit Life's High NotesExplore the Trumpet
The trumpet is made of brass tubing bent into a rough spiral. Although the bore is roughly cylindrical, it is more precisely a complex series of tapers, smaller at the mouthpiece receiver and larger just before the flare of the bell begins. Careful design of these tapers is critical to the intonation of the instrument. Sound is produced by blowing air through closed lips, producing a "buzzing" sound into the mouthpiece and starting a standing wave vibration in the air column inside the trumpet. The player can select the pitch from a range of overtones or harmonics by changing the lip aperture. There are three piston valves, each of which increases the length of tubing when engaged, thereby lowering the pitch. The first valve lowers the instrument's pitch by a whole step (2 semitones), the second valve by a half step (1 semitone), and the third valve by one-and-a-half steps (3 semitones). When a fourth valve is present, as with some piccolo trumpets, it lowers the pitch a perfect fourth (5 semitones). Used alone and in combination these valves make the instrument fully chromatic, i.e., able to play all twelve pitches of Western music. The sound is projected outward by the bell.
More About the Trumpet
The mouthpiece has a circular rim which provides a comfortable environment for the lips' vibration. Directly behind the rim is the cup, which channels the air into a much smaller opening (the backbore or shank) which tapers out slightly to match the diameter of the trumpet's lead pipe. The dimensions of these parts of the mouthpiece affect the timbre or quality of sound, the ease of playability, and player comfort. A wider and deeper cup are often best suited for a fuller, more expansive sound, while shallow-cupped "pea-shooter" mouthpieces can facilitate execution in the extreme high register. A larger rim allows for more assured striking of the notes; a smaller rim improves endurance but decreases flexibility.
New School of Music teaches trumpet lessons at our music schools located in Buford, GA 30518, Dunwoody/North Fulton, GA 30338, Lilburn, GA 30047, Johns Creek, GA 30097, Fayetteville, GA 30215, and Flowery Branch, GA 30542. We are the southeast's leading music conservatory with over 2000 students enrolled! Our schools serve the communities of Dunwoody, Sandy Springs, Chamblee, Doraville, Roswell, Alpharetta, Norcross, Snellville, Stone Mountain, Lawrenceville, Duluth, Sugar Hill, Suwanee, Lawrenceville, Oakwood, Dacula, Gainesville, Winder, Braselton, Jackson, Pendergrass, Auburn, Winder, Gwinnett County, Hall County, Dekalb County, Fulton County, Jackson County, Banks County, Madison County, and Franklin County. Rent a school band or orchestra instrument, shop online, and more.
The smallest trumpets are referred to as piccolo trumpets. The most common of these are built to play in both B♭ and A, with separate leadpipes for each key. The tubing in the B♭ piccolo trumpet is exactly one-half the length of that in a standard B♭ trumpet. Piccolo trumpets in G, F and even high C are also manufactured, but are rarer. Many players use a smaller mouthpiece on the piccolo trumpet. Because of the smaller mouthpiece size, endurance is often limited and the sound production technique is different from that used on the B♭ trumpet. Almost all piccolo trumpets have four valves instead of the usual three: the fourth valve takes the instrument down in pitch, usually by a fourth, to facilitate the playing of lower notes. Maurice Andre, Wynton Marsalis andHakan Hardenberger are some of the more well-known piccolo trumpet players.
Trumpets pitched in the key of G are also called sopranos, or soprano bugles, after their adaptation from military bugles. Traditionally used in drum and bugle corps, sopranos have featured both rotary valves and piston valves.
The bass trumpet is usually played by a trombone player, being at the same pitch and using a similar mouthpiece.
The slide trumpet is a B♭ trumpet that has a slide instead of valves. It is similar to a soprano trombone. The first slide trumpets emerged during the Renaissance, predating the modern trombone, and are the first attempts to increase chromaticism on the instrument. Slide trumpets were the first trumpets allowed in the Christian church.[1]
The pocket trumpet is a compact B♭ trumpet. The bell is usually smaller than a standard trumpet, and the tubing is more tightly wound, to reduce the instrument size without reducing the total tube length. Its design is not standardized, and the quality of various models varies greatly. It can have a tone quality and projection unique in the trumpet world: a warm sound and a voice-like articulation. Unfortunately, since a major part of pocket trumpet models suffer from poor design as well as cheap and sloppy manufacturing, the intonation, tone color and dynamic range of such instruments are severely hindered.
There are also rotary-valve, or German, trumpets, as well as alto and Baroque trumpets.
The trumpet is often confused with its close relative, the cornet, which has a more conical tubing shape compared to the trumpet's more cylindrical tube. This, along with additional bends in the cornet's tubing, gives the cornet a slightly mellower tone, but the instruments are otherwise nearly identical. They have the same length of tubing and, therefore, the same pitch, so music written for cornet and trumpet is interchangeable. Another relative, the flugelhorn, has tubing that is even more conical than that of the cornet, and an even richer tone. It is sometimes augmented with a fourth valve to improve the intonation of some lower notes.
In medieval times, trumpet playing was a guarded craft, its instruction occurring only within highly selective guilds. The trumpet players were often among the most heavily guarded members of a troop, as they were relied upon to relay instructions to other sections of the army. Improvements to instrument design and metal making in the late Middle Ages and Renaissance led to an increased usefulness of the trumpet as a musical instrument. The development of the upper, "clarino" register, by specialist trumpeters, would lend itself well to the Baroque era, also known as the "Golden Age of the natural trumpet." The melody-dominated homophony of the classical and romantic periods, relegated the trumpet to a secondary role by most major composers. An exception is Haydn's Trumpet Concerto written for keyed trumpet in 1796. The trumpet was slow to adopt the modern valves (invented around the mid 1830s), and its cousin, the cornet would take the spotlight as solo instrument for the next hundred years. Crooks and shanks (removable tubing of various lengths) as opposed to keys or valves, were standard, into the first part of the 20th century.
The Arabic word for trumpet was naffir. The Spanish used the Arabic name al naffir and changed it into anafil, while the French gave the trumpet its own name, buisine, derived from the Latin word buccina. (Trompet.nl, 2005)
Today, the trumpet is used in nearly all forms of music, including classical, jazz, rock, blues, pop, ska, polka and funk. Among the great modern trumpet players are Maurice André, Louis Armstrong, Miles Davis, Dizzy Gillespie, Arturo Sandoval, Jon Faddis,Maynard Ferguson, Adolph "Bud" Herseth, Wynton Marsalis, Lee Morgan, Philip Smith, Doc Severinsen and James Morrison. See20th century brass instrumentalists for a more comprehensive list.
As with all musical instruments, there are physical challenges to playing the trumpet. The knowledge of operating the instrument is called technique. Almost all aspects of technique are controversial, since different people have different problems to overcome, and different successes to celebrate.
"There are 3 layers of abdominal muscles from the groin to the sternum (breastplate); there are 2 layers of muscles (inner and outer) in between the ribs; there are back muscles from the lumbar region upward to the shoulders; there is the diaphragm just below the lung sacs; and there are muscles coming-down diagonally from behind the ear which connect to the top of the rib cage . When a person does a "forced exhalation", the entire family is activated as a "one- family" movement. They ALL simultaneously increase their tension levels in order to raise the internal compression level (PSI) in the lung chambers. This moves the air FASTER which is one of the first necessary things that must occur when a player moves "upward" in the register.
The area that the player needs to become aware of is NOT in the diaphragm but in the center of the abdominal muscles, approximately near the navel. The body has a natural way of centering itself if you only just try to blow suddenly as if spitting a piece of rice or blowing out a candle. By learning to control the variance of tension, either isometric for holding a compression level or by tightening and relaxing the degrees of tension based upon what you are playing, one discovers that it is really the abdominal support that controls the air. This ab support certainly influences the diaphragm but it is NOT the diaphragm alone that moves the air. It is the FAMILY of muscles, all guided by the abdominal centering." (Bobby Shew)
As the lower abdominal muscles pull up and in; the internal organs are all slightly moved the same direction. These push against the diaphragm and pressurize the air by making the chest cavity smaller. The farther you move the abdominal muscles and the faster that you do it; then the stronger the air support is.
Strengthening the embouchure (muscles of the face, sometimes "chops" in common slang). Some commonly accepted ways to do this are:
Lip slurs: playing exercises that change notes without changing the fingering. The notes must be produced by the embouchure along with changes in air flow.
Tonguing exercises: playing exercises that have many notes started with a sharp definition (usually a "dah" or "tah" sound) produced by the tongue.
Practicing on the mouthpiece: playing exercises on the mouthpiece only, without the trumpet. Without the resonating chamber of the rest of the instrument, the pitch may vary much more freely, so control must be developed. This may also help to reduce the amount of pressure used. This was a favorite exercise of the famous Rafael Mendez.
Playing high: playing in the upper register, at the top of the player's comfortable range. This can increase one's range, as the higher notes become easier.
Reducing pressure: To play higher notes on the trumpet requires compression of the embouchure (the muscles of the face and lips), as well as air pressure to provide the energy for the vibration of the lips. One way to compress the lips is to press the mouthpiece firmly onto them, but this is counterproductive in the long run. Blood cannot flow into the lips, so they become stiff and unable to vibrate. More importantly, the muscles needed to play correctly without pressure are not strengthened.
Playing softly: Another useful exercise is to play very softly. Herbert L. Clarke was the first person to really teach soft playing. In the first exercise in the Clarke Technical Studies, he recommends playing pianissimo and decreasing the volume until the sound is barely audible. This helps the player focus the lip aperture to the point at which there is just a thread of air coming through.
Lip buzzing: Buzzing the lips without the mouthpiece or instrument is a helpful exercise for increasing stamina in the embouchure. Air is blown through pursed lips as one would do when playing the trumpet, keeping the air flow constant. Lip buzzing also helps a player to develop a sense of pitch without the help of the valves.
Long Tones: Playing soft notes for an extened period of time to help muscle memory and intonation.
pressing the mouthpiece to the lips (as explained above)
playing with an uneven balance of pressure between the upper and lower lips (see double buzz)
inflating cheeks when blowing (although this is debated - some of the greatest jazz trumpeters such as Dizzy Gillespie, Harry James, and Charlie Shavers were known for it and it is essential to circular breathing, a technique necessary to play continuously for any significant period of time. Most players, however, will achieve better results when the cheeks are not inflated)
playing with poor posture
closing the throat (tensing of the throat muscles, resulting in partially restricting the air flow.)
having an overly tense posture (producing notes becomes easier when the body, especially the embouchure and shoulders, are relaxed. The player should try not to extend the arms more than 90 degrees from the elbows)
Keeping neutral corners. Keep the corners of the mouth in a neutral position to avoid stretching or compressing the aperture too much.
Finding the ideal mouthpiece placement for maximum vibration. Players often experiment with different angles and positions until the best possible one for vibration is found. This position may vary in extreme registers.
Note that the fundamental of each overtone series does not exist - the series begins with the first overtone. Notes in parentheses are the sixth overtone, representing a pitch with a frequency of seven times that of the fundamental; while this pitch is close to the note shown, it is slightly flat and use of those fingerings is therefore discouraged.
The fingering schema arises from the length of each valve's tubing (air passing through longer lengths of tubing produces a lower pitch). Valve "1" increases the tubing length enough to lower the pitch by one whole step, valve "2" by one half step, and valve "3" by one and a half steps. This schema and the nature of the overtone series create the possibility of alternate fingerings for certain notes. For example, third-space "C" can be produced with no valves engaged (standard fingering) or with valves 2-3. Also, any note produced with 1-2 as its standard fingering can also be produced with valve 3 - each drops the pitch by 1-1/2 steps. Alternate fingerings may be used to improve facility in certain passages. Extending the third valve slide when using the fingerings 1-3 or 1-2-3 further lowers the pitch slightly to improve intonation.
Wikipedia:Text of the GNU Free Documentation License
New School of Music teaches trumpet lessons at our music schools located in Buford, GA 30518, Dunwoody/North Fulton, GA 30338, Lilburn, GA 30047, Johns Creek, GA 30097, Fayetteville, GA 30215, and Flowery Branch, GA 30542. We are the southeast's leading music conservatory with over 2000 students enrolled! Our schools serve the communities of Dunwoody, Sandy Springs, Chamblee, Doraville, Roswell, Alpharetta, Norcross, Snellville, Stone Mountain, Lawrenceville, Duluth, Sugar Hill, Suwanee, Lawrenceville, Oakwood, Dacula, Gainesville, Winder, Braselton, Jackson, Pendergrass, Auburn, Winder, Gwinnett County, Hall County, Dekalb County, Fulton County, Jackson County, Banks County, Madison County, and Franklin County. Rent a school band or orchestra instrument, shop online, and more.
Types of trumpets
The most common type is the B♭ trumpet, but C, D, E♭, E, F, G and A trumpets are also available. The C trumpet is most commonly used in orchestral playing, where its slightly smaller size gives it a brighter, more lively sound than the B♭ trumpet. Because music written for early trumpets required the use of a different trumpet for every key (they did not have valves and were therefore not chromatic), and also because a player may choose to play a particular passage on a different trumpet from the one indicated on the written music, orchestra trumpet players are generally adept at transposing music at sight. Being able to play music written for the B♭ trumpet on the C trumpet, and vice-versa, is fairly common. Each trumpet's range extends from the written F♯ immediately below Middle C, up to about three octaves higher. Standard repertoire rarely calls for notes beyond this range, and the fingering tables of most method books peak at the C (high C) two octaves above middle C. Fingerings above this are generally the same as those for the notes an octave lower. Several trumpeters have achieved fame for their proficiency in the extreme high register, among them Arturo Sandoval, Dizzy Gillespie, Bill Chase, James Morrison and Maynard Ferguson, who helped make well-known the term double high C to describe the next octave above high C. It is also possible to produce pedal tones below the low F♯, although this technique is more often encountered as a sound-production exercise rather than as a written trumpet part. It is possible to play up to 3 octaves below middle C.The smallest trumpets are referred to as piccolo trumpets. The most common of these are built to play in both B♭ and A, with separate leadpipes for each key. The tubing in the B♭ piccolo trumpet is exactly one-half the length of that in a standard B♭ trumpet. Piccolo trumpets in G, F and even high C are also manufactured, but are rarer. Many players use a smaller mouthpiece on the piccolo trumpet. Because of the smaller mouthpiece size, endurance is often limited and the sound production technique is different from that used on the B♭ trumpet. Almost all piccolo trumpets have four valves instead of the usual three: the fourth valve takes the instrument down in pitch, usually by a fourth, to facilitate the playing of lower notes. Maurice Andre, Wynton Marsalis andHakan Hardenberger are some of the more well-known piccolo trumpet players.
Trumpets pitched in the key of G are also called sopranos, or soprano bugles, after their adaptation from military bugles. Traditionally used in drum and bugle corps, sopranos have featured both rotary valves and piston valves.
The bass trumpet is usually played by a trombone player, being at the same pitch and using a similar mouthpiece.
The slide trumpet is a B♭ trumpet that has a slide instead of valves. It is similar to a soprano trombone. The first slide trumpets emerged during the Renaissance, predating the modern trombone, and are the first attempts to increase chromaticism on the instrument. Slide trumpets were the first trumpets allowed in the Christian church.[1]
The pocket trumpet is a compact B♭ trumpet. The bell is usually smaller than a standard trumpet, and the tubing is more tightly wound, to reduce the instrument size without reducing the total tube length. Its design is not standardized, and the quality of various models varies greatly. It can have a tone quality and projection unique in the trumpet world: a warm sound and a voice-like articulation. Unfortunately, since a major part of pocket trumpet models suffer from poor design as well as cheap and sloppy manufacturing, the intonation, tone color and dynamic range of such instruments are severely hindered.
There are also rotary-valve, or German, trumpets, as well as alto and Baroque trumpets.
The trumpet is often confused with its close relative, the cornet, which has a more conical tubing shape compared to the trumpet's more cylindrical tube. This, along with additional bends in the cornet's tubing, gives the cornet a slightly mellower tone, but the instruments are otherwise nearly identical. They have the same length of tubing and, therefore, the same pitch, so music written for cornet and trumpet is interchangeable. Another relative, the flugelhorn, has tubing that is even more conical than that of the cornet, and an even richer tone. It is sometimes augmented with a fourth valve to improve the intonation of some lower notes.
History
The oldest trumpets date back to 1500 B.C.E. and earlier. The bronze and silver trumpets from Tutankhamun's grave in Egypt,bronze lurs from Scandinavia, and metal trumpets from China date back to this period.[2] Trumpets from the Oxus civilization (3rd millennium B.C.E.) have decorated swellings in the middle, yet is made out of one sheet of metal, a technical wonder.[3] The earliest trumpets were signaling instruments used for military or religious purposes, rather than music in the modern sense. "The sound of these instruments was described as terrible, that is, producing terror, and was compared to the braying of an ass."[4] The modern bugle continues the signaling tradition, with different tunes corresponding to different instructions, but the advent of radiomade its use is more ceremonial.In medieval times, trumpet playing was a guarded craft, its instruction occurring only within highly selective guilds. The trumpet players were often among the most heavily guarded members of a troop, as they were relied upon to relay instructions to other sections of the army. Improvements to instrument design and metal making in the late Middle Ages and Renaissance led to an increased usefulness of the trumpet as a musical instrument. The development of the upper, "clarino" register, by specialist trumpeters, would lend itself well to the Baroque era, also known as the "Golden Age of the natural trumpet." The melody-dominated homophony of the classical and romantic periods, relegated the trumpet to a secondary role by most major composers. An exception is Haydn's Trumpet Concerto written for keyed trumpet in 1796. The trumpet was slow to adopt the modern valves (invented around the mid 1830s), and its cousin, the cornet would take the spotlight as solo instrument for the next hundred years. Crooks and shanks (removable tubing of various lengths) as opposed to keys or valves, were standard, into the first part of the 20th century.
The Arabic word for trumpet was naffir. The Spanish used the Arabic name al naffir and changed it into anafil, while the French gave the trumpet its own name, buisine, derived from the Latin word buccina. (Trompet.nl, 2005)
Today, the trumpet is used in nearly all forms of music, including classical, jazz, rock, blues, pop, ska, polka and funk. Among the great modern trumpet players are Maurice André, Louis Armstrong, Miles Davis, Dizzy Gillespie, Arturo Sandoval, Jon Faddis,Maynard Ferguson, Adolph "Bud" Herseth, Wynton Marsalis, Lee Morgan, Philip Smith, Doc Severinsen and James Morrison. See20th century brass instrumentalists for a more comprehensive list.
Technique
Trumpeter performing with the United States Air Force Band in EuropeAs with all musical instruments, there are physical challenges to playing the trumpet. The knowledge of operating the instrument is called technique. Almost all aspects of technique are controversial, since different people have different problems to overcome, and different successes to celebrate.
Several important aspects of technique
Breathing properly (abdominal support of air). "This is one of the areas of brass playing that causes a great deal of confusion. Much discussion about the importance of the diaphragm has sent many a player down the road to confusion, inability, and bleeding lips. The upper part of the torso contains a large family of muscles that all have been designed to function in a teamwork fashion specially when we do something requiring forced exhalation, eg. blowing out candles, spitting something out of our mouth, or blowing into a wind instrument."There are 3 layers of abdominal muscles from the groin to the sternum (breastplate); there are 2 layers of muscles (inner and outer) in between the ribs; there are back muscles from the lumbar region upward to the shoulders; there is the diaphragm just below the lung sacs; and there are muscles coming-down diagonally from behind the ear which connect to the top of the rib cage . When a person does a "forced exhalation", the entire family is activated as a "one- family" movement. They ALL simultaneously increase their tension levels in order to raise the internal compression level (PSI) in the lung chambers. This moves the air FASTER which is one of the first necessary things that must occur when a player moves "upward" in the register.
The area that the player needs to become aware of is NOT in the diaphragm but in the center of the abdominal muscles, approximately near the navel. The body has a natural way of centering itself if you only just try to blow suddenly as if spitting a piece of rice or blowing out a candle. By learning to control the variance of tension, either isometric for holding a compression level or by tightening and relaxing the degrees of tension based upon what you are playing, one discovers that it is really the abdominal support that controls the air. This ab support certainly influences the diaphragm but it is NOT the diaphragm alone that moves the air. It is the FAMILY of muscles, all guided by the abdominal centering." (Bobby Shew)
As the lower abdominal muscles pull up and in; the internal organs are all slightly moved the same direction. These push against the diaphragm and pressurize the air by making the chest cavity smaller. The farther you move the abdominal muscles and the faster that you do it; then the stronger the air support is.
Strengthening the embouchure (muscles of the face, sometimes "chops" in common slang). Some commonly accepted ways to do this are:
Lip slurs: playing exercises that change notes without changing the fingering. The notes must be produced by the embouchure along with changes in air flow.
Tonguing exercises: playing exercises that have many notes started with a sharp definition (usually a "dah" or "tah" sound) produced by the tongue.
Practicing on the mouthpiece: playing exercises on the mouthpiece only, without the trumpet. Without the resonating chamber of the rest of the instrument, the pitch may vary much more freely, so control must be developed. This may also help to reduce the amount of pressure used. This was a favorite exercise of the famous Rafael Mendez.
Playing high: playing in the upper register, at the top of the player's comfortable range. This can increase one's range, as the higher notes become easier.
Reducing pressure: To play higher notes on the trumpet requires compression of the embouchure (the muscles of the face and lips), as well as air pressure to provide the energy for the vibration of the lips. One way to compress the lips is to press the mouthpiece firmly onto them, but this is counterproductive in the long run. Blood cannot flow into the lips, so they become stiff and unable to vibrate. More importantly, the muscles needed to play correctly without pressure are not strengthened.
Playing softly: Another useful exercise is to play very softly. Herbert L. Clarke was the first person to really teach soft playing. In the first exercise in the Clarke Technical Studies, he recommends playing pianissimo and decreasing the volume until the sound is barely audible. This helps the player focus the lip aperture to the point at which there is just a thread of air coming through.
Lip buzzing: Buzzing the lips without the mouthpiece or instrument is a helpful exercise for increasing stamina in the embouchure. Air is blown through pursed lips as one would do when playing the trumpet, keeping the air flow constant. Lip buzzing also helps a player to develop a sense of pitch without the help of the valves.
Long Tones: Playing soft notes for an extened period of time to help muscle memory and intonation.
Avoiding bad habits
As is the case in learning any instrument, bad habits can develop that can ultimately lead to slower improvement, a poorly developed sound, lessened endurance, or even pain. Common bad habits include:pressing the mouthpiece to the lips (as explained above)
playing with an uneven balance of pressure between the upper and lower lips (see double buzz)
inflating cheeks when blowing (although this is debated - some of the greatest jazz trumpeters such as Dizzy Gillespie, Harry James, and Charlie Shavers were known for it and it is essential to circular breathing, a technique necessary to play continuously for any significant period of time. Most players, however, will achieve better results when the cheeks are not inflated)
playing with poor posture
closing the throat (tensing of the throat muscles, resulting in partially restricting the air flow.)
having an overly tense posture (producing notes becomes easier when the body, especially the embouchure and shoulders, are relaxed. The player should try not to extend the arms more than 90 degrees from the elbows)
Keeping neutral corners. Keep the corners of the mouth in a neutral position to avoid stretching or compressing the aperture too much.
Finding the ideal mouthpiece placement for maximum vibration. Players often experiment with different angles and positions until the best possible one for vibration is found. This position may vary in extreme registers.
Fingering
On any trumpet, cornet, or flugelhorn, pressing the valves indicated by the numbers below will produce the written notes shown - "OPEN" means all valves up, "1" means first valve, "1-2" means first and second valve simultaneously and so on. The concert pitch which sounds depends on the transposition of the instrument. Engaging the fourth valve, if present, drops any of these pitches by a perfect fourth as well. Within each overtone series, the different pitches are attained by changing the embouchure, or lip positionand tightness, along with increasing air velocity. Standard fingerings above high C are the same as for the notes an octave below (C♯ is 1-2, D is 1, etc.).Note that the fundamental of each overtone series does not exist - the series begins with the first overtone. Notes in parentheses are the sixth overtone, representing a pitch with a frequency of seven times that of the fundamental; while this pitch is close to the note shown, it is slightly flat and use of those fingerings is therefore discouraged.
The fingering schema arises from the length of each valve's tubing (air passing through longer lengths of tubing produces a lower pitch). Valve "1" increases the tubing length enough to lower the pitch by one whole step, valve "2" by one half step, and valve "3" by one and a half steps. This schema and the nature of the overtone series create the possibility of alternate fingerings for certain notes. For example, third-space "C" can be produced with no valves engaged (standard fingering) or with valves 2-3. Also, any note produced with 1-2 as its standard fingering can also be produced with valve 3 - each drops the pitch by 1-1/2 steps. Alternate fingerings may be used to improve facility in certain passages. Extending the third valve slide when using the fingerings 1-3 or 1-2-3 further lowers the pitch slightly to improve intonation.
Wikipedia:Text of the GNU Free Documentation License