led to ever increasing demands on the
orchestra. The prelude developed into the operatic overture whose
business it became to prepare the spectator for what followed. That
music was capable of conveying an impression in her own tone-language
was apparent, and in due time the symphony rose majestic from the forge
of genius.

Prominent among the materials welded into it was the dance of obscure
origin. As the vocal aria was the result of the simple folk-song
combined with the intense craving of song's master molders for
individual expression, so instrumental music striving to walk alone,
without support from words, gained vital elements through the discovery
that various phases of mental disposition might be indicated by
alternating dance tunes differing in rhythm and movement, according to
Nature's own law of contrasts. That unity of purpose was essential to
the effectiveness of the diversity was instinctively discerned.

The touch of authority was given to this kind of music, during the last
two decades of the seventeenth century, by Arcangelo Corelli when he
presented in the camera, or private apartment, of Cardinal Ottoboni's
palace, in Rome, his idealized dance groups, thoroughly united by
harmony of mood, yet affording a wholly new tone-picture of this mood in
each of several movements. These compositions were usually written for
the harpsichord and perhaps three instruments of the viol order, the
master himself playing the leading melody on the violin. He called them
sonatas from sonare, to sound, a name originally applied to any piece
that was sounded by instruments, not sung by the human voice. They
prefigured the solo sonata, the entire class of chamber music named from
the place where they were performed, and the symphony which is a sonata
for the orchestra. Absolute music was set once for all on the right path
by them. They ushered in a new era of Art.

Purcell, in England, Domenico Scarlatti and Sammartini, in Italy, the
Bachs, in Germany, and others continued to fashion the sonata form. It
ceased to be a mere grouping of dances, the name suite being applied to
that, and struck out into independent excursions in the domain of
fancy. The prevailing melody of its monophonic style proved suitable to
furnish a subject for the most animated discussion. Three contrasting
movements were adopted, comprising a summons to attention, an appeal to
both intellect and emotions, and a lively reaction after excitement.