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The modes where the scales form successive perfect quartes, are
the following:
1) "Rast", 2) "Shur", and 3) "Segah".
In the scales consisting of successive series of perfect quartes,
the main quarte marks are the tones, which take the position of
the first degree in the tetrachord 1-1-1/2.
These degrees are called the main tones, and they implement tonic
function in the mode "Rast".
1.
Composing music in the mode "Rast"
A.
Diapason of the mode scale"Rast"
Three
equal tetrachords structured by formula 1 - 1 - 1/2
and connected by chain combination form the scale of the "Rast"
mode. The first degree of
the medial tetrachord in this scale is a modal tonic.
With the first
octave tonic
do the scale of the "Rast" is presented in
the following way:
Â.
Modal functions of degrees and permissible leaps
All
the degrees of the "Rast" modal
scale
are subordinated
to the tonic. These tones are intended to "serve" the
tonic and intensify its dominant position in the melody. Therefore,
the
third, the
quarte, and
the quinte
leaps are not permitted from the each degree. For example: a quarte
leap from the sub-mediant to the supertonic la-rå serves
the tonic, but a quarte leap from the subtonic to the third of
the tonic si-mi has a divergent intonation with a tendency
to transform the third of the tonic mi into an independent
tonic, that is why this leap is forbidden.
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1-st degree functions in the above mode scale "Rast"as
a lower quarte of the tonic. Gradual move from this degree
is possible in the ascending direction. The lower quarte is
a foothold for the leap into the tonic and supertonic. |
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2-nd
degree functions as a mediant of the tonic. It prepares a
supertonic and the keynote subtonic: upper one with a leap
to the major second, and lower one with a leap to the quarte.
Leaps from this degree are possible directly to the tonic
and supertonic of the keynote. |
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3-rd
degree functions as a keynote subtonic . Before the tonic
leap it can step one second downwards. From the subtonic it
is possible to make a leap only to the supertonic. |
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4-th
degree, the main tone, functions as a tonic. The tonic allows
leaps in the ascending direction to the third, the upper
quarte, the quinte and the supertonic of the quinte; in
the descending direction to the mediant and the lower quarte.
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5-th
degree functions as a supertonic. Leaps from this degree are
possible upwards - to the tonic quarte and quinte, downwards
- to the subtonic, to the tonic mediant and to the lower quarte
of the tonic. |
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6-th
degree functions as a tonic third. Leaps from this degree
are allowed: upwards -to the tonic quinte, downwards - to
the tonic. |
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7-th
degree functions as an upper quarte of the tonic. Leaps
from this degree are allowed: upwards -to the supertonic
of the quinte and downwards - to the supertonic of the keynote
and to the tonic.
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8-th
degree functions as a tonic quinte. Leaps from this degree
are allowed: downwards - to the third, to the supertonic of
the keynote and to the tonic. |
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9-th
degree functions as a supertonic of the keynote quinte. Only
one leap downwards to the supertonic of the keynote is allowed
from this degree. |
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10-th
degree acts as a boundary tone of the mode scale. Leaps from
this degree are not allowed, gradual movement is possible
only in the descending direction. |
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