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Chordophones Physics of Music PHY103 Tradeoffs in chordophones Strings only High tension means a lot of stress on the instrument. More massive strings have lower pitches under lower tension However thick strings don’t bend very easily

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Physics of Music PHY103

tradeoffs in chordophones strings only
Tradeoffs in chordophonesStrings only
  • High tension means a lot of stress on the instrument.
  • More massive strings have lower pitches under lower tension
  • However thick strings don’t bend very easily
    • Loss of high frequencies leading to dull or soft timbre.
    • Shift of overtones sharpwards
piano spectrum
Piano spectrum








Higher harmonics are higher than multiples of fundamental

Why? Wave equation requires more energy for shorter waves – non-linear wave equation on string

are these frequency shifts important
Are these frequency shifts important?

Butler(example 2.4).

a) Piano playing C4

b) Piano playing C4 but the partials have been lowered by digital processing so that their frequencies are exact integer multiples of the fundamental.

Pair of tones repeated 3 times.

loose strings
Loose strings
  • Violin D string tuned to an A?
  • bowed and plucked
bass strings
Bass strings
  • If you lower the tension too much the tension changes during plucking or hammering. The pitch changes after the pluck. The strings flop around leading to buzzing and fast damping.
  •  Low notes then requires thick and heavy strings (metal ones) to prevent these problems.
  • Wound strings help reduce problem of loss of high frequencies. Problems with wound strings: damage to fret-board and fingers particularly for fretless basses.
  • To keep corrosion from reducing high frequency response  plastic covering. However stretching of plastic may damp string motion faster.
  • If the tension is too low then the string will hit the finger board. This is less of a problem for a harp but is a big problem for a guitar or lute.
soprano strings
Soprano strings
  • Require light strings and high tension (for a given tension).
  • Metallic strings are tiny and kill your fingers. Many steel string lutes/guitars are not plucked by hand.
  • Gut or nylon strings are softer but damp faster and are less bright.
tradeoffs in the strings
Tradeoffs in the strings
  • Length/tension/density – ease of play, position of plucking, having strings of different notes on the same keyboard or fret-board, strength of instrument.
  • String composition

– metallic – less damping but heavier, harsher and more damaging to fingers and fret-boards

– Gut or nylon – softer/duller but lighter and damping faster

  • A string by itself is not a very good radiator – it has a small surface area.
  • To increase volume the vibration must be coupled to something with a larger surface area.
  • Box: guitar/zither - vibration passes through bridge– faces of the box vibrate.
  • The surfaces of the box vibrate in modes as does the air inside.
amplification continued
Amplification (continued)
  • Box with holes – air moves in and out

(violin, guitar)

  • Box with a membrane (African lutes) vibrations excited in the membrane too.

The string excites harmonics, some are amplified more than others depending on the coupling of the string to box and the way the box resonates.

violin spectrum
Violin spectrum

note the envelope!

spectrum is remarkably harmonic

cello spectrum
Cello spectrum
  • Again note envelope
open strings vs fingered on violin
Open strings vs fingered on violin
  • open string has stronger high frequency harmonics
guitar spectrum and decay
Guitar spectrum and decay

At different times

piano action
Piano Action
  • While the 88 key board had been fully developed in the 15th century the “piano-forte” action was introduced by Christofori in the early 18th century.
  • Originally hammers were covered with soft leather
modern piano action
Modern Piano Action
  • Modern piano action is modeled after Crhistofori’s.
  • Pianists criticize electric keyboards and pianos because they fail to have the sensitivity and response of the piano action
string decay rates
String decay rates
  • The more strings, the louder the sound.
  • Coupling between strings can influence how sound is transferred to soundboard
  • Slower decays with 2+ strings
composers write for available instruments
Composers write for available instruments

Moonlight Sonata Beethoven

  • Evgeny Kissin playing a modern Steinway
  • Gayle Martin Henry playing a piano from around 1805 by the Viennese maker Caspar Katholni

This clip from:

the comparison from the posted article by Jan Swafford!

Modern pianos have bigger keyboards, longer sustain and more uniform timbre across registers

Composers used the longer sustain and differences in timber as effects

examples of chordophones box zither santoor india
Examples of ChordophonesBox Zither- Santoor India
  • Box zither – trapezoid box with many parallel strings, strings are struck
  • Santoor (Indian)

Music taken from CD Musical instruments of the World 1990 CNRS

vietnamese board zither
Vietnamese Board Zither
  • 16 steel strings above an oblong convex sound box.
  • Strings are plucked and pressed to change the pitch
class projects 2005 before
Class projects 2005 , before
  • little koto
  • washtub bass
african lute chad
African LuteChad
  • Skin below the strings on the gourd.
  • Gourd resonator
tar lute from azerbaijan
Tar: Lute from Azerbaijan
  • Belly is covered with ox pericardium membrane
  • 24 movable frets of gut?
harp ngombi central africa
Harp –ngombi Central Africa
  • plucked soft gut strings
kora guinea
  • ox tendon strings slid up and down for tuning
  • notched bridge
mbela musical bow central africa
Mbela- Musical Bow Central Africa
  • What is the resonant cavity?
role of sustain in varying how plucked instruments are played
Role of sustain in varying how plucked instruments are played
  • Metallic strings with long sustain must be damped, harder to play (use pluckers)
  • Gut strings with short sustain are strummed rapidly with fingers
sounding the string
Sounding the string
  • Plucking finger/plucker

Sound is influenced by position of plucker

  • Hammering

Sound is influenced by weight of hammer, material of hammer and leverage of hammer.

  • Bowed –stick/slip continuous excitation. Ability to control sound quality during the entire tone

For plucked and hammered tones, there is no control after the note sounds

hammered plucked bowed

Which one is which and how might you expect the sound would be different?

amplification via pickups
Amplification via Pickups
  • Magnetic pickups
  • Contact pickups
  • Air pickups (aka microphones)
  • Optical pickups
magnetic pickups
Magnetic pickups
  • coil typically thousands of winds with thin magnet wire and with a central iron core. Resonant frequency of pickup tuned with capacitance of wires and other stuff to be near ear sensitivity peak (few 2kHz).
  • Pickups combined in series and with opposite phases so hum is cancelled  humbucker
  • they work near vibrating metal (strings, gongs …)

Disadvantages: noise pickup, need vibrating metal

Advantages: interesting sound quality, no need for sound board, good sustain

contact pickups
Contact Pickups
  • Typically using piezo-electric material
  • Often mounted on or near bridge of a stringed instrument. Ineffective in wind instruments unless allowed to move in the air

Advantages: flat frequency response, very cheap, resistant to noise pickup, no need for sound board

Disadvantages: possibly less dynamic range, pickups up surface noise, clicks, knocks, scrapes, plucking

air pickups
Air pickups
  • Microphones
  • Most natural sound
  • Sensitive to feedback