TA212
The Technology of Music
Steve Wells
Producing Musical
Sounds
TA212: Block 3, Chapter 1
Musical Instruments
guitar
harp
plucked
piano
keyboard
synthesiser
struck
violin
electronic
bowed
trombone
strings
cello
instruments
wind
side drum
percussion
woodwind
untuned
tom tom
tuned
xylophone tubular bells
brass
tuba
trumpet
clarinet
flute
recorder
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
Musical Instruments
• Something which produces sound
– Compressions and rarefactions in the air
• Predictable output
– Pitch
– Volume
– Rhythm
• Controllable by a player
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
Sound Production
• Need to be able to put energy into the system
(excitation)
– No energy – no noise!
• Something to resonate
– Primary vibrator provides pitch
• String, air column
– Secondary vibrators
• The rest of the instrument
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
Sound Excitation
• Putting in energy to make a sound
– Blowing into a wind instrument
– Plucking a string
– Bowing a string
– Beating a drum
• Energy in a burst
– Transient sound
• Energy continuous
– Sustained sound
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
Nodes and Antinodes
• Waves can “interfere” producing locations where
there is no change
• These locations are fixed despite the fact that the
waves are moving
• A place where Nothing is changing is called a Node
• An Antinode is where something is changing
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
Types of Node
• A place where Nothing is changing is called a Node
• Two types of Node:
– A Pressure Node occurs where there is no change of
pressure
• for example, at the open end of a wind instrument
– A Displacement Node occurs where there is no
displacement (movement) of the vibrating medium
• for example, at the bridge of a stringed instrument
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
Standing Waves
• The sequence of nodes and antinodes form a
standing wave
• When a string is vibrating:
N
displacement
node
A
displacement
antinode
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
N
displacement
node
Standing Waves
• The sequence of nodes and antinodes form a
standing wave
• When an air column is is vibrating:
A
displacement
antinode
N
displacement
node
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
A
displacement
antinode
Woodwind Instruments
TA212: Block 3, Chapter 2
Wind Harmonics
open pipe
stopped pipe
NOTE: A conical pipe (such as an oboe) behaves
like a pipe open at both ends
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
“Bernoulli” Principle
Air blowing over a surface
creates suction
…either the air moves...
…or the surface moves!
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
Oboe Reed
air
air
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
air
Recorder Mouthpiece
air
Suction due to the
Bernoulli Effect.
air
The air stream
passes to one side
of the edge, is
sucked onto the
edge and
overshoots.
This repeats...
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
Wind Pitch
• Length of the pipe determines the pitch
– (also temperature)
• Change pitch by:
– Changing the length
• Brass instruments
– Finger holes
• Woodwind
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
Wind Pitch
• Pitch of a pipe depends on two things:
– Length (L) : shorter = higher
– Speed of Sound (v) : higher temperature = higher
• For a pipe open at both ends:
v
f1 
2L
• For a stopped pipe (open at one and closed at the
other):
v
f1 
4L
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
Fingerholes
Effective length depends on the position and size of the hole
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
Fingerholes
physical end
of the pipe
no fingerhole
small fingerhole
large fingerhole
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
displacement
antinodes
The displacement
antinodes are at
different possible
positions due to
different end
effects.
Recorder Mouthpiece
air
displacement
antinode
Due to end effects, the displacement antinode is
effectively inside the air channel
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
End Correction
• Effective length of a pipe is greater than the physical
length of the pipe.
physical length
effective length
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
End Correction
radius (r)
end correction (e)
e  0. 6  r
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
Question: Length of a Pipe
A pipe stopped at one end sounds the note A4 (440Hz)
as its first harmonic. If the pipe has a diameter of
20mm, what is the physical length of the pipe?
Assume the speed of sound to be 340m/s.
TA212 - Block 3
Brass Instruments
TA212: Block 3, Chapter 3
What is a Brass Instrument
• Not always made of brass!!
• Key idea is the way the sound is made
– Lip reed
– Players lips vibrate within the mouthpiece to excite the
air column
– Similar to the way a reed excites the air column in and
oboe or clarinet
TA212 - Block 3 - Chapter 3 - Brass Instruments
Parts of a Brass Instrument
TA212 - Block 3 - Chapter 3 - Brass Instruments
Types of Brass Instrument
• Mainly Cylindrical
– Natural Trumpets and Trombones
• Mainly Conical
– Horns
• Combination of Cylindrical and Conical
– Trumpet
– Cornet
(A Cornet has a longer conical section than a Trumpet)
TA212 - Block 3 - Chapter 3 - Brass Instruments
The Air Column
• The bell is open
• The mouthpiece behaves like a closed end
• However...
– Fundamental not used (usually out of tune)
– The flare on the bell raises the pitch of the lower
harmonics
– The mouthpiece lowers the pitch of the upper
harmonics
• The effect is to get an almost complete harmonic
series (the fundamental is missing)
TA212 - Block 3 - Chapter 3 - Brass Instruments
Tuning
• Harmonics are used more than with woodwind
– Bugle only uses harmonics
• Tuning
– Slide
– Valve
– Finger holes
• like woodwind
• not used in modern orchestral instruments
TA212 - Block 3 - Chapter 3 - Brass Instruments
Valves
TA212 - Block 3 - Chapter 3 - Brass Instruments
Stringed Instruments
TA212: Block 3, Chapter 3
String Harmonics
• Many different standing waves
• The sounds they produce are the harmonics of the
string.
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
String Pitch
• Pitch of a string depends on three things:
– Length (L) : shorter = higher
– Tension (T) : tighter = higher
– Mass per unit length ( ) : lighter = higher
TA212 - Block 3 - Chapter 1 - Producing Musical Sounds
Question: String Tension
A Fender Stratocaster has a string length of 648mm.
The sixth string (lowest pitch) has a mass per unit
length of 6.79x10-3 kg/m. It is tuned so that its first
harmonic is E2 (82.4Hz).
What is the tension in the string?
f1
T
L
µ
TA212 - Block 3
frequency
tension
length
mass per unit length
Violin Family
• Many medieval instruments were bowed
– Rebec
– Vielle
• The modern violin appears in late 17th century
• Four sizes
Lowest note
Tuned in
Violin
G3
Fifths
Viola
C3
Fifths
Cello
C2
Fifths
Double Bass
E1
Fourths
TA212 - Block 3 - Chapter 3 - Stringed Instruments
Violin Bridge
TA212 - Block 3 - Chapter 3 - Stringed Instruments
Lutes and Guitars
• Descended from arabic instrumets
– Through Moorish Spain or, perhaps, the Crusades
– “Lute” comes from “al‘ud”
• Plucked and Strummed
• Strings stretched along a neck
– Usually fretted
• Many variations throughout the Middle and Far East
– Long and short necks
– “2” to “12 or more” strings
TA212 - Block 3 - Chapter 3 - Stringed Instruments
Classical Guitar
• Modern form developed in 19th
– Torres developed the larger body and fan strutting
– Tarrega and, later, Segovia showed what the
instrument was capable of
• Six strings
– E3, A3, D4, G4, B4, E5
TA212 - Block 3 - Chapter 3 - Stringed Instruments
Percussion
TA212: Block 3, Chapter 5
Drum Vibration Modes
TA212 - Block 3 - Chapter 5 - Percussion
Drum Frequencies
1
2.29
1.59
2.65
TA212 - Block 3 - Chapter 5 - Percussion
2.13
2.91
Other Drums
• Bass Drum
– Two heads
– Often one head is tighter than the other so that the
frequencies do not correspond
– Untuned
• Snare Drum
– Wires across one head causes a rattle as the head
moves
TA212 - Block 3 - Chapter 5 - Percussion
Simple Gongs and Cymbals
• Modes of Vibration similar to a circular drum skin
• Low frequencies dominate first, then higher
frequencies take over
• Untuned
TA212 - Block 3 - Chapter 5 - Percussion
Circular Plate Vibration Modes
TA212 - Block 3 - Chapter 5 - Percussion
Circular Plate Frequencies
1
1.73
2.33
TA212 - Block 3 - Chapter 5 - Percussion
3.91
Oriental Gong
• Shape forces the first two
harmonics to have a
frequency ratio of 2:1
• Other harmonics
effectively not present
• Tuned
TA212 - Block 3 - Chapter 5 - Percussion
Vibrating Bars
• Glockenspiel, Xylophone etc
TA212 - Block 3 - Chapter 5 - Percussion
Vibrating Bars
TA212 - Block 3 - Chapter 5 - Percussion
Vibrating Bars
The instrument is
“tuned” because felt
supports go here to
damp all but the
fundamental mode
of vibration
TA212 - Block 3 - Chapter 5 - Percussion
Question: Rectangular Bar
A glockenspiel bar is made out of steel whose Young’s
Modulus is 201x109 N/m2 and whose density is 7800
kg/m3. The bar is 5mm thick and 111mm long.
What frequency will it sound?
f1
E

t
L
E t
f1  1.03
2
 L
TA212 - Block 3
frequency
Young’s modulus
density
thickness
length
Percussion Pitch
• Modes of vibration do not form a harmonic series
• No well defined pitch, but...
– Timpani
• Air damping within the instrument shifts the modes of
vibration to produce a harmonic series
– Glockenspiel
• Supports damp out the unwanted modes of vibration
– Oriental Gong
TA212 - Block 3 - Chapter 5 - Percussion
Keyboard Instruments
TA212: Block 3, Chapter 6
Keyboards
• Standard interface to many different ways to make a
sound
– clavichord
– harpsichord/virginal/spinet
– piano
– organ
– piano accordion
– electronic keyboard
– celesta
TA212 - Block 3 - Chapter 6 - Keyboard Instruments
Clavichord
damping
tangent
fulcrum
bridge
• Unfretted Clavichord - one string for each note
• Fretted Clavichord - several notes on each string
TA212 - Block 3 - Chapter 6 - Keyboard Instruments
Plucked Strings
Harpsichord
Virginal
Spinet
TA212 - Block 3 - Chapter 6 - Keyboard Instruments
Piano
• Hammers hit the string
• The hammer needs to:
– hit the string at a controllable speed
– have a clean rebound
– not hit the string twice
• Modern mechanism invented by Cristofori in 1720
TA212 - Block 3 - Chapter 6 - Keyboard Instruments
Piano Key Levers
force
f
e
effect
e
effect
f
force
e
speed factor 
f
e
f
TA212 - Block 3 - Chapter 6 - Keyboard Instruments
force
effect
Cristofori Action
TA212 - Block 3 - Chapter 6 - Keyboard Instruments
Organ
TA212 - Block 3 - Chapter 6 - Keyboard Instruments
Organ
pipe
roller
valve
tracker
air in
windchest
key
TA212 - Block 3 - Chapter 6 - Keyboard Instruments
Organ Stops
• An Organ Stop selects a bank of pipes
• The length is an indication of pitch, not physical
length
– 8ft is normal pitch (A4=440Hz)
– 4ft sounds an octave higher
• A stop labelled “8ft stopped”
– normal pitch made with stopped pipes
– NOT 8ft pipes stopped to produce the effect of 16ft
pipes.
TA212 - Block 3 - Chapter 6 - Keyboard Instruments
Question: Organ Stops
A pipe organ is tuned in concert pitch. The key
normally sounding the A above middle C (A4) is
pressed.
What note will sound when each of the following
stops are used.
8’ diapason
4’ diapason
16’ stopped
Why will the tone of the 16’ stopped pipes differ from
the others?
TA212 - Block 3
The Voice
TA212: Block 3, Chapter 7
Anatomy
TA212 - Block 3 - Chapter 7 - The Voice
Voice and Clarinet
sound source
pitch
timbre
clarinet
reed
air column
fixed
voice
vocal folds
vocal folds
TA212 - Block 3 - Chapter 7 - The Voice
Variable
(vocal tract)
Graphic Equaliser
• The vocal tract can
emphasise different
frequencies
• Like a graphic equaliser…
• Different vowels are
produced by emphasising
different frequencies
TA212 - Block 3 - Chapter 7 - The Voice
Vowels
• Shape of the vocal tract
• Each shape emphasises different frequencies
• The frequencies which are emphasised are called
Formants
TA212 - Block 3 - Chapter 7 - The Voice
Spectrogram
frequency
formants
time
TA212 - Block 3 - Chapter 7 - The Voice
Formant Chart
second formant
• Vowels can be
characterised by the
frequencies of the
first two formants
first formant
TA212 - Block 3 - Chapter 7 - The Voice
Singer’s Formant
• Formants pulled closer together create an increase in
loudness
– not more energy
– more efficient use of existing energy
• Distorts the vowels
– consonants become important for intelligibility
TA212 - Block 3 - Chapter 7 - The Voice
Electronic Instruments
TA212: Block 3, Chapter 8
Types of Electronic Instrument
• Electroacoustic
– sound source is mechanical (string of electric guitar)
• Electromechanical
– replays physical representations of sounds (Hammond
organ)
• Electronic
– sound is created from an electronic circuit (synthesiser)
TA212 - Block 3 - Chapter 8 - Electronic Instruments
Electromagnetic Induction
electricity
magnetism
motion
• Given any two, the third is produced
electricity + magnetism = motion (electric motor)
magnetism + motion = electricity (generator)
TA212 - Block 3 - Chapter 8 - Electronic Instruments
Electric Guitar
• Electroacoustic
• Electromagnetic induction
– “movement + magnetism = electricity”
TA212 - Block 3 - Chapter 8 - Electronic Instruments
Hammond Organ
• Electromechanical
• Electromagnetic induction
– “movement + magnetism = electricity”
– the lobes on the spinning wheel disturb the magnetic
field creating a current in the wire
spinning wheel
magnet
wire
TA212 - Block 3 - Chapter 8 - Electronic Instruments
Moog Synthesiser
• Electronic
• No moving parts!
• Analogue
TA212 - Block 3 - Chapter 8 - Electronic Instruments
BBC Radiophonic Workshop
TA212 - Block 3 - Chapter 8 - Electronic Instruments
Contacting Me
• Phone
01454-850379
• Email
s.wells@.open.ac.uk
• Web
http://www.stevesphotosite.co.uk/ta212
TA212 The Technology of Music
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TA212 The Technology of Music
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