The beginnings and development of a New Zealand music: The life ...

However, most of these F minor statements are achieved through the use
of a non-triadic bass-note, and usually appear as F minor seventh chords.
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Thus, up until bar 16, the 'key' of the piece remains ambiguous.
Throughout these opening bars, Lilburn has constructed his material
above what basically amounts to two pedal points. The first of these is
based on B-flat, alternating with, but dominating, touches of an F pedal.
The second of these (from bar 9) is a C-based pedal.
In the absence of
a firm feeling of 'key', these pedals help establish tonal centres for
the bars in which they are stated. As the scale notes remain the same
above each of these tonal centre pedals, the music assumes a modal
flavour:
B-flat dorian for bars 1-8, and C phrygian for bars 9-\5. The
'movement away from the C pedal at bar 15 can be viewed as a preparation
for the cadence onto the new F-based pedal of bar 16.
As much of Lilburn's music otherwise shows use ot modal resources,
it would seem sensible to view such tonally ambiguous passages in
harmonic-modal terms, rather than conventional major-minor 'key' terms.
John Vincent in his book The Diatonic Modes in Modern Music l
neatly rationalises this alternative method of analysis. Vincent
identifies the properties of each individual mode as being classifiable
into two categories or 'indices'. He terms these categories 'ordinal'
indices and 'lateral' indices.
An ordinal index comprises modes that share the same seven
diatonic pitches, or, in other words, share the same key signatures
or accidentals. A lateral index comprises modes that share the same
tonic. Thus, D dorian and A aeolian share the same ordinal index of
modality, whilst D dorian and D aeolian share the same lateral index.
Under this system, a shift in one tonic can freely occur to any
of six other tonics without chromatic alteration to the scale notes
employed.
modality.
Vincent calls this a modulation within the ordinal index of
To elaborate, consider the C major scale. This is called a C
scale because the tonic (or centre of gravity) of the scale is C.
called major because of the characteristic ordering of the scale notes
into interval steps (ascending) away from the tonic of tone, tone,
semitone, tone, tone, tone, and'semitone.
However, if the tonic (or
It is
centre of gravity) of this particular set of scale notes was to become D
(perhaps through frequent stressing), then this would alter the
characteristic ordering of scale notes into interval steps away, from the
Hollywood, California, Curlew Music Publishers revised ed., 1974,
394 pp.