How brass instruments work Al Cannon
What gives the trumpet its clarion ring
and the tuba its gut-shaking
“omm pah pah?”
And what makes the trombone so jazzy?
The answer lies not in the brass
these instruments are made of,
but in the journey air takes
from the musician’s lungs
to the instrument’s bell.
Like any sound, music consists
of vibrations traveling through air.
Instruments are classified based on
how those vibrations are produced.
Percussion instruments are struck.
String instruments are plucked or bowed.
Woodwinds have air blown
against a reed or sharp edge.
For brass instruments, however,
the vibration come directly
from the musician’s mouth.
One of the first things a brass player
must learn is to breathe in deeply,
until every possible particle of air
is crammed into the lungs.
Once all that air is inside,
it must come out through the mouth,
but there, an internal battle takes place
as the musician simultaneously tries
to hold their lips firmly closed
while blowing enough air
to force them open.
The escaping air meets resistance
from the lip muscles,
forms an opening called the aperture
and creates the vibration
that brass players call “the buzz.”
When a mouthpiece is held up
to those vibrating lips,
it slightly refines the buzz,
amplifying the vibration
at certain frequencies.
But things get really interesting
depending on what instrument
is attached to that mouthpiece.
A brass instrument’s body
is essentially a tube
that resonates with the air
column blowing through it.
The way that sound waves
travel through this column
forms a limited pattern of pitches
known as the harmonic series,
with notes spaced far apart
at the lower end,
but coming closer together
as the pitch increases.
The musician can alter
the pitch of the note
through slight contractions of the lips
and alterations to air volume and speed.
Slower, warm sighing air
produces lower pitches,
and faster, cool, flowing air
produces higher pitches in the series.
But any single harmonic series has gaps
where pitches are missing
and the versatility of brass instruments
lies in their ability to switch
between multiple series.
On instruments like the trumpet,
valves can be lowered
to increase the length of tubing
the air travels through,
while on a trombone,
this is done by extending its slide.
Lengthening the tube stretches
the vibrating air column,
reducing the frequency of vibrations
and resulting in a lower pitch.
This is why the tuba,
the largest brass instrument,
is also the one capable of playing
the lowest notes.
So changing the instrument length
shifts its harmonic series,
while slight variations of the air flow
and the player’s lips
produce the different notes within it.
And those notes finally emerge through
the flared bell opening at the end.
What started as a deep breath
and a vibrating buzz on the lips
has now been transformed
into a bold and brassy tune.
The musician’s skillful manipulation
of every part of the process
from lungs,
to lips,
to the mouthpiece,
to the instrument itself creates
an amazing palette of pitches
that can be heard in musical genres
across the globe.
By harnessing the power
of natural resonance
in a flexible and controllable way,
brass instruments are great examples
of the fusion of human creativity
with the physics of our world.