Transcript The Overtone Series

The Overtone Series
 Derivation of Tonic Triad – Tonal Model
 Timbre
 Chord Spacing
Pitch
 The perception of pitch is a result of
vibration.
 A body such as a string or column of air
vibrates at a particular frequency producing
a characteristic pitch.
 E.g. When a string vibrates at 440 cycles
per second (Hz), the note A is perceived.
Fundamental Pitch
 The perceived pitch is known as the
fundamental pitch.
 The string does not vibrate at the same
speed throughout its length.
Overtones
 Halfway through the length of the string, it
barely vibrates at all producing a node.
 This divides the string into two shorter
strings lengths that each vibrate at twice the
speed of the complete string.
 This produces another pitch an octave
above the fundamental known as an
overtone.
Many Overtones
 The string also vibrates over 1/3 of its
length, 1/4 of its length and so on.
 The result is that there are many overtones
produced above the fundamental pitch.
 These overtones are too soft to be
individually perceived but are nevertheless
present.
Overtone Series
 The overtone pitches result in the following
series.
Tonic and Dominant
 Notice that the first two overtones
correspond to the Tonic and Dominant Scale
Degrees of the fundamental pitch’s scale.
 This accounts for the importance of tonic
and dominant in tonal music as well as the
tonal desire to move by fifths.
Tonic Triad
 Notice also that the fundamental and first
five overtone pitches produce the tonic
triad.
 This is often used to explain the tonal
tendency to always want to return to the
tonic triad.
Timbre
 Timbre refers to “colour” of sound.
 A clarinet and saxophone can play the same
pitches but will sound different because of
their timbre.
 Timbre results from the fact that
instruments produce overtones with
different amplitudes (volumes).
Clarinet vs. Saxophone
 The clarinet timbre differs from the
saxophone because of the relative strengths
of their overtones.
Flutey vs. Nasally
 Generally, an instrument that produces
stronger overtones will have a more nasal
sound (oboe).
 An instrument that has weaker overtones
will sound more pure (flute).
 The stronger overtones account for the
greater penetrating ability of the oboe but
also for its reduced ability to blend with
other instruments.
Spacing
 Traditional spacing of chords usually
follows the overtone series.
 In other words, low pitches are separated by
wider gaps than higher pitches.
 This is because the lower pitches have more
perceptible overtones (within hearing
range).
 A low pitch triad will therefore sound
muddy (low triad on the piano).
Spacing Effects
 While the traditional model spaces notes
according to the overtone series, interesting
effects and chord colours can be created by
counteracting the overtone series.
 A very dark sound can result from
combining low instruments with small
intervals.