Idiophones:

1

• Idiophones
• these are instruments that are self resonant,
  that is when they are struck or rubbed they will
  produce a note or sound by themselves, this is
  typically any percussion instrument without a
  head or skin
• Membranophones
• any instrument which has a head or skin stretched
  across a frame that can be struck, this includes
  all types of drums

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Percussion

• Idiophones
• Pitched
• Xylophone, tubular bells, bells
• unpitched
• Cymbal, triangle
• membranophones
• pitched
• Kettle drums, tabla
• unpitched.
• Bass drum, snare drum

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remember

• A vibrating or oscillating source
• A method of transmitting or coupling the
  oscillator to the air usually termed as a
  resonator

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Main points of a drum

• A frame
• A membrane stretched across the frame the
  membrane is assumed to be freely suspended, and
  clamped at its outer edge
• tensioning device

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• The modes of vibration when struck can be very
  complex
• vibrate in circular and radial modes
• Two dimensional surface
• mode numbers refer to vibration modes
• the first number is the radial mode
• the second indicates the circular mode

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MODE 0 1
7
Mode 1 1
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More modes of vibration
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• Theoretical relationship of modes
• To the fundamental
• MODE Freq
• 0 1 1
• 1 1 1.59
• 2 1 2.14
• 0 2 2.3
• 3 1 2.65
• 1 2 2.92
• 4 1 3.16

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• Many complex modes
• Most of which are not harmonically related
• Actual pitch of harmonics (partials) can be very
  difficult to determine
• A strong fundamental unsupported by harmonics
  can be hard to determine.
• Depends on the tension of the head, the mass of
  the head and the nature of the shell over which
  it is stretched.

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Timpani

• When the drum has a metal shell with a
  hemispherical shape, it is called a timpani, then
  a definite pitch can be determined
• Originally calfskin head but almost exclusively
  now using plastic skins
• pedal operated tuning mechanism

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• Originally a military instrument capable of high
  acoustic power output

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Analysis of Timpani

• Things to note
• one side of the membrane is moving in the air in
  the kettle
• damps the vibration of the head
• this tends to lower the principle frequencies
• The enclosed air has resonance's of its own
• these vibrations will interact with the modes of
  vibration

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• Drum is struck using sticks with felt pads.
• A skilled player is very specific about the
  striking point.
• Analysis of G2

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Other common membranophones

• Orchestral bass drum
• large cylindrical shell (up to 1.2m diameter and
  0.45m across
• heads on both sides
• sits on a stand in the upright position
• head modes are complex (two heads and enclosed
  air mass)

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Snare Drum

• Snare drum
• 0.25m to 0.35m diameter 0.1m to 0.25m depth
• bottom head has ribbon of steel strings (snare)
• snares rattles when top head is struck
• head modes are complex (two heads and enclosed
  air mass)

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• DBSPL _at_1metre
• High Low Range
• Timpani 122 36 86
• Snare drum 117 60 57
• Bass drum 122 43 79
• Cymbals 116 50 66

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Directional properties

• Can be complex !
• Is generally best to have only one head facing a
  microphone due to partial cancellations (phase
  reversals)

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Idiophones

• Two main categories
• subdivide each category into pitched and non
  pitched
• Metallophones
• metal bars, rods, tubes, cymbals, gongs and
  plates etc
• Xylophones
• any type of sounding wood

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MarimbaTuned xylophone
21
Marimba

• Suspended wooden bars
• tuned cylindrical resonator below each bar
• arranged like a piano keyboard
• very fast decay - resonator used to extend decay
  of sound

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Vibraphone tuned metallophone
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vibraphone

• Suspended metal bars
• tuned cylindrical resonator below each bar
• arranged like a piano keyboard
• on top of each resonator is a circular stop
• motor driven
• alternately stops and opens the resonator

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analysis

• Vibrate in very complex manner
• twisting, bending (torsional bending)
• greatly affected by
• method of striking
• position of strike

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Frequency range

• Instruments vary a great deal
• Vibraphone F4 to F7
• Marimba C4 to C7

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analysis

• Very little published information about the
  directional properties and acoustical power
  output of idiophones
• the normal rules of sound radiation will apply

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Ensembles and The Orchestra

• The baroque period (1600 - 1750) Chamber music
  took many forms many ensembles using either The
  Continuo
• A wooden piped organ
• which was a keyboard instrument with a bass part
  played by bassoon or cello
• continuo was the usual accompaniment for one or
  two solo instruments

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• harpsichord
• or later, as it evolved, the piano
• string quartet. Two violins, a cello to provide
  the bass and a viola to fill in the mid range.
• Woodwind and brass ensembles were also very
  popular

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Famous composers of the baroque period (1600-1750)

• Antonio Vivaldi (1678-1741)
• Johann Sebastian Bach (1685-1750)
• George Frederic Handel (1685-1759)

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classical era (1750 - 1830)

• larger string ensemble with varying woodwind and
  brass sections
• evolution of the modern symphony orchestra

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Famous composers of the classical period (1750 -
1830)

• Beethoven (1770-1827)
• Haydn (1732-1809
• Mozart (1756-1791)

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romantic period of the early 1800's

• Berlioz (1803-1869)
• Wagner (1813-1883)
• formed large ensembles of instruments and voices,
  resembling today's concert orchestra

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• Strauss (1864-1949)
• Stravinsky (1882-1971)
• Mahler (1860-1911)
• extended the components and skill required in
  the orchestra

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Typical layout of modern orchestra
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• changed over the years
• still remains subject to change
• according to number of players and the
  requirements of the composer and conductor

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Classical Period Romantic Period Modern
Period 6 1st Violins 10 1st Violins 14 1st
Violins 6 2nd Violins 10 2nd Violins 14 2nd
Violins 4 Violas 8 Violas 10 Violas 4
Cellos 8 Cellos 10 Cellos 2 Basses 6
Basses 9 Basses 2 Flutes 2 Flutes 3 Flutes 2
Oboes 1 Piccolo 1 Piccolo 2 Clarinets 2
Oboes 3 Oboes 2 Bassoons 1 Cor anglais 1 Cor
anglais 2 Horns 2 Clarinets 3 Clarinets 2
Trumpets 1 Bass Clarinet 1 Bass Clarinet 1
Timpani 2 Bassoons 3 Bassoons 1
Contrabassoon 1 Contrabassoon 4 Horns 4
Horns 3 Trumpets 3 Trumpets 3 Trombones 3
Trombones 1 Tuba 1 Tuba 1 Timpani 1
Timpani 2 Percussion 3 Percussion 2
Harps 1 Keyboard
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Sound levels

• The dynamic range and spectra of an orchestra is
  obviously related to its components, but a member
  of the audience in a concert hall would expect to
  experience levels around 70 to 90 dB SPL

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Conclusions

• Sampling
• recording
• live or in a studio
• midi tracks
• wavetable or soundfont
• equalisation
• synthesis
• orchestral instruments are still heavily used in
  modern recording