egourotchka_ [[263-264]]--Soprano and Alto.

* _The Christmas Night_ [[78-80]]--Alto and Tenor.

* _Legend of Kitesh_ [[338]]--Tenor and Bass.

Voices related in thirds;

3 [Sopr. M.-sopr. Ten. Bar.
[M.-sopr., C.-alto, Bass, Bass,

may move in unison, in thirds and sixths, and admit very largely of
the crossing of parts. Separation by more than an octave must only be
momentary, and is generally to be avoided.

_Examples:_

* _The Tsar's Bride_ [[174]]--Sopr. and Mezzo-sopr.

* _Tsar Saltan_ [[5-6]]--Sopr. and Mezzo-sopr.

In the case of voices related in twelfths: 12 [Sopr./Bass, intervals
approaching one another do not create a good effect, for this
transplants the deeper voice into the upper register and _vice versa_.
Singing in unison is no longer possible, and thirds are to be avoided;
the use of sixths, tenths and thirteenths is recommended. The voices
will often be separated by more than a twelfth and crossing of parts
is out of the question.

_Example:_

* _Tsar Saltan_ [[254-255]].

Relationship in tenths 10 [Sopr./Bar. or M.-sopr./Bass is fairly
common. The explanations given above are also applicable in this case.

_Example:_

_Snegourotchka_ [[291-300]] (cf. extract, Ex. 118) Sopr. and Bar.

The use of similar voices in pairs: Sopr./Sopr., Ten./Ten. entails
singing in unison and thirds. They should rarely be separated beyond a
sixth, but crossing of parts is inevitable, as otherwise the resultant
volume of tone would be too weak.

_Note._ Other possible combinations: C.-alto/Bar.,
M.-sopr./Ten., call for no special remarks.

_Examples:_

* _The May Night_, Act I pp. 59-64--Mezzo-sopr. and Tenor.

* _Sadko_ [[322-324]]--Mezzo-sopr. and Tenor.

As a general rule, writing for two voices is only successful when the
progression of parts is clear, when discords are prepared by a common
note, or are the outcome of conveniently separated movement and
correctly resolved. Empty intervals of fourths and perfect fifths,
elevenths and twelfths should be avoided on the strong beats of a bar,
especially on notes of some value. If, however, one of the voices
assumes a melodic character, the other forming the harmonic
accompaniment in declamatory style, it is not absolutely necessary to
avoid the intervals mentioned above.

_Note._ It is not within the scope of the present work to
consider the writing of vocal parts in closer detail. This
question must be left to th