PH 105
Dr. Cecilia Vogel
Lecture 17
OUTLINE
Resonances of string instruments
Brass Instruments
Lip reed
Closed tube
Effect of bell
Registers
timbre
Playing scales
String Instrument Review
Fundamental freq —pitch
determined by string.
many harmonics produced by string, too.
Spectrum — timbre
Resonances of bridge, plates, air cavity.
enhance certain harmonics.
Timbre Demo
A-string
Expect strong
110 &220 near resonances (fig 10.31)
play C3 (131 Hz): 1st harm ___, 2nd ___
G-string
Expect strong fundamental and 2nd harm?
196 Hz and 392 Hz near resonances at 200 &
400 Hz (folk only)
B-string
f1= 246.94 Hz, ___ and ___ harmonics
near 250 Hz and 550 Hz resonance of classical
Brass Instruments
An instrument is considered to be in the
brass family if
the source of disturbance for the sound
is a
i.e. the lips buzz in the mouthpiece to
excite sound waves in the air inside
Sound of a brass instrument is affected by
sound source (_____), resonances
(___________), and radiation (_____)
Feedback
Can control pitch of lip reed
by changing
Hard to do with precision.
Even harder to maintain.
Once lips have started the air vibrating
the pressure variations in the air
This is called positive feedback.
Air Column Resonances
The lip end of a brass instrument
is a
The cylindrical tube of a brass instrument
WOULD resonate at freq’s
nv
fn 
Where
4L
v = speed of sound in air
L = length of tube
n = only odd integers
BUT…..
Bell Effect
Adding a bell and mouthpiece
makes the instrument longer,
________ all the resonant freq’s.
But the high freq resonances are affected
more,
so the resonances get
Bell Effect
1
3
5
Resonances without bell
and mouthpiece
ratio 5/3
= 1.67
Resonances with bell
and mouthpiece
ratio 3/2
= 1.5
Bell Effect
Adding carefully tuned bell and mouthpiece
makes resonances other than the lowest
approximately ,
even and odd,
of a
The “lowest” note of brass instrument,
is not the fundamental frequency,
but 2nd partial.
Lowest resonance— called “pedal tone”
not often used, overtones not harmonic.
Open Notes of Brass
B3b (233 Hz) uses 2nd resonance of tube
played note
(fundamental
of lip buzz)
harmonics
of played note
(harmonics in
lip buzz)
Open Notes of Brass
F4 uses 3rd tube resonance 349 Hz (which
is a fifth above B3b)
played
note
harmonics
of played note
Open Notes of Brass
B4b uses 4nd tube resonance at 466 Hz
(which is an octave above B3b)
played
note
harmonics
of played note
Registers
Can play B3b, F4, and B4b on trumpet
by exciting different
of the same
These are the open notes of three
different registers
higher registers have weaker overtones
Bugle can only play these notes.
Slides
Trombone can play whole chromatic scale
by changing the length of the tube.
Slide a piece of tube out making it
To go one semitone lower, the length of the
tube should increase by
1/18 its current length.
The lower you go, the
fig 11.11
Seven Positions
There are seven positions for trombone slide
Position 7 gives you E2
in the lowest
Positions 6-1 let you go up 1-6 semitones.
What if you wanted to go up 7 semitones?
That’s a
Can play that in 7th position
Using slide in 2nd register,
then in upper register.
gets you all the way up to B3b
Valves
Trumpet can play whole chromatic scale
Pressing a valve brings an additional piece of
tube into the airway
making it
One valve makes it one
brings in extra 5.9% (about 1/18) of tube length.
Another makes it two
brings in extra 12.2 % of tube length.
Yet another makes it three
brings in extra 18.9% of tube length.
Three Valves
With only three valves, how do you go
down more than 3 semitones?
one + three =
two + three =
one + two +three =
7 semitones is a
can be played in
Four semitones is more than
logarithmic, not linear.
Third valve tubing may have a slide, so it can
be adjusted. Or you can adjust lip freq.
Brass Demo
Listen to timbre. Observe spectrum.
Play in different registers.
What technique is used?
What intervals can be played with same
slide or valve position?
(expect 2nd, 3rd & 4th harmonics; factors of
3/2 or a perfect fifth and of 2 or an octave)
Change of timbre with register
Play chromatic scale using slide/valves.
which slide positions are closer together?
Why?
Summary
Closed tube resonances,
are changed by bell & mouthpiece,
brass instrument resonates at
2nd, 3rd, 4th, etc harmonics of missing fund.
registers:
3rd harmonic is up a fifth from 2nd
4th harmonic is up an octave from 2nd
Trombone adds length with 7 positions of
slide.
Trumpet adds length with 3 valves.