22
1 The Musician’s Experience of Brass Instruments
muscle active in inspiration is the diaphragm, which separates the chest cavity
from the abdominal cavity. When the diaphragm contracts, it pulls the floor of
the chest cavity downwards; the resulting increase in lung volume is enhanced by
intercostal muscles which pull the ribs upwards and outwards. When these muscles
are relaxed, the elasticity of the lungs causes them to contract, raising the internal
lung pressure, and resulting in an outflow of air. The increase in lung pressure can
be enhanced by the action of abdominal muscles which push the chest floor upwards
and a second group of intercostal muscles which pull the rib cage downwards.
To maintain a smooth flow of air, the effects of these expiratory muscles can be
partially counteracted by the first group of inspiratory intercostal muscles. The use
of respiratory muscles in brass performance is discussed further in Sect. 6.3.4.
Achieving good control of blowing pressure and air flow is essential for any
wind instrumentalist, and there has been some disagreement over the best way to
teach this aspect of brass playing technique (Dudgeon et al. 1997). Some instructors
focus on the regulation of the mouth pressure by the respiratory muscles, while
others encourage students to think more about the creation of a smooth air flow into
the instrument. The flow of air into the mouthpiece during the sounding of a note
is not strictly speaking smooth, since the lip aperture through which the air passes
is opening and closing regularly at the frequency of the note. The modulated flow
which leaves the lips can be thought of as a steady mean flow plus an acoustic flow
fluctuating around this mean value at the playing frequency. Although it may be
pedagogically helpful to encourage students to focus on a column of air moving
through the instrument and out of the bell, the work of the air flow in generating
sound is complete once it has passed through the lips and entered the mouthpiece.
Even if the flow is then diverted so that it does not pass into the instrument
(Sect. 2.1.5), acoustic pressure waves transmit the sound from the mouthpiece down
the air column to the bell and beyond.
1.2.9 Resistance and Playing Effort
The resistance to the steady flow of air through a tube is defined as the pressure
difference between its ends divided by the rate of air flow through it. This steady
flow resistance increases as its internal diameter is reduced, so a trumpet mouthpiece
with a throat diameter of 3.7 mm has a much higher steady flow resistance than a
tuba mouthpiece with a throat diameter of 8.4 mm. The difference in steady flow
resistance can be qualitatively experienced by taking a deep breath and allowing the
breath to exhale naturally through open lips into each mouthpiece. The initial lung
pressure and the volume of air taken in during inspiration will be approximately
the same in each case; expiry through the tuba mouthpiece will be complete in
around a second, but will last several seconds through the trumpet mouthpiece.
When the mouthpieces are inserted into their respective instruments, the expiry
times are increased by the additional resistance of the instrument tubing, but the
same qualitative difference is evident.
1 The Musician’s Experience of Brass Instruments
muscle active in inspiration is the diaphragm, which separates the chest cavity
from the abdominal cavity. When the diaphragm contracts, it pulls the floor of
the chest cavity downwards; the resulting increase in lung volume is enhanced by
intercostal muscles which pull the ribs upwards and outwards. When these muscles
are relaxed, the elasticity of the lungs causes them to contract, raising the internal
lung pressure, and resulting in an outflow of air. The increase in lung pressure can
be enhanced by the action of abdominal muscles which push the chest floor upwards
and a second group of intercostal muscles which pull the rib cage downwards.
To maintain a smooth flow of air, the effects of these expiratory muscles can be
partially counteracted by the first group of inspiratory intercostal muscles. The use
of respiratory muscles in brass performance is discussed further in Sect. 6.3.4.
Achieving good control of blowing pressure and air flow is essential for any
wind instrumentalist, and there has been some disagreement over the best way to
teach this aspect of brass playing technique (Dudgeon et al. 1997). Some instructors
focus on the regulation of the mouth pressure by the respiratory muscles, while
others encourage students to think more about the creation of a smooth air flow into
the instrument. The flow of air into the mouthpiece during the sounding of a note
is not strictly speaking smooth, since the lip aperture through which the air passes
is opening and closing regularly at the frequency of the note. The modulated flow
which leaves the lips can be thought of as a steady mean flow plus an acoustic flow
fluctuating around this mean value at the playing frequency. Although it may be
pedagogically helpful to encourage students to focus on a column of air moving
through the instrument and out of the bell, the work of the air flow in generating
sound is complete once it has passed through the lips and entered the mouthpiece.
Even if the flow is then diverted so that it does not pass into the instrument
(Sect. 2.1.5), acoustic pressure waves transmit the sound from the mouthpiece down
the air column to the bell and beyond.
1.2.9 Resistance and Playing Effort
The resistance to the steady flow of air through a tube is defined as the pressure
difference between its ends divided by the rate of air flow through it. This steady
flow resistance increases as its internal diameter is reduced, so a trumpet mouthpiece
with a throat diameter of 3.7 mm has a much higher steady flow resistance than a
tuba mouthpiece with a throat diameter of 8.4 mm. The difference in steady flow
resistance can be qualitatively experienced by taking a deep breath and allowing the
breath to exhale naturally through open lips into each mouthpiece. The initial lung
pressure and the volume of air taken in during inspiration will be approximately
the same in each case; expiry through the tuba mouthpiece will be complete in
around a second, but will last several seconds through the trumpet mouthpiece.
When the mouthpieces are inserted into their respective instruments, the expiry
times are increased by the additional resistance of the instrument tubing, but the
same qualitative difference is evident.