hat of the preceding, and of the one
maintained by the violas, the conductor marks _two divided beats_ for
the long bar, by two equal gestures down, and two others up:--

[Illustration]

The two large gestures divide the long bar in half, and explain its
value to the hautboys, without perplexing the violas, who maintain the
brisk movement, on account of the little gesture which also divides in
half their short bar.

From bar No. 3, the conductor ceases to divide thus the long bar by 4,
on account of the triple rhythm of the melody in 6/8, which this gesture
interferes with. He then confines himself to marking the two beats of
the long bar; while the violas, already launched in their rapid rhythm,
continue it without difficulty, comprehending exactly that each stroke
of the conductor's stick marks merely _the commencement_ of their short
bar.

This last observation shows with what care dividing the beats of a bar
should be avoided when a portion of the instruments or voices has to
execute triplets upon these beats. The division, by cutting in half the
second note of the triplet, renders its execution uncertain. It is even
necessary to abstain from this division of the beats of a bar just
before the moment when the rhythmical or melodic design is divided by
three, in order not to give to the players the impression of a rhythm
contrary to that which they are about to hear:--

[Illustration]

In this example, the subdivision of the bar into six, or the division of
beats into two, is useful; and offers no inconvenience _during bar
No. 1_, when the following gesture is made:--

[Illustration]

But from the beginning of bar No. 2 it is necessary to make only the
simple gestures:--

[Illustration]

on account of the triplet on the third beat, and on account of the one
following it which the double gesture would much interfere with.

In the famous ball-scene of Mozart's _Don Giovanni_, the difficulty of
keeping together the three orchestras, written in three different
measures, is less than might be thought. It is sufficient to mark
downwards each beat of the _tempo di minuetto_:--

[Illustration]

Once entered upon the combination, the little allegro in 3/8, of which a
whole bar represents one-third, or one beat of that of the minuetto, and
the other allegro in 2/4, of which a whole bar represents two-thirds, or
two beats, correspond with each other and with the principal theme; while
the whole proceeds withou