an for a large concert hall.

The words _trio_ and _quartet_ are also applied to vocal works
for three and four voices respectively, these having no
relation whatsoever to the sonata as described above. The word
_trio_ is also applied to the middle section of minuets,
scherzas, marches, etc., the term originating in the old usage
of writing this part for three instruments only.

155. A _concerto_ is a sonata for a solo instrument with orchestral
accompaniment, the form being usually somewhat modified so as to adapt
it to a composition in which there must necessarily be opportunity for
a good deal of technical display. There are usually but three movements
in the _concerto_.

The great majority of _concertos_ are for piano and orchestra,
but examples of concertos for violin, cello, flute, oboe, and
other solo instruments (all with orchestral accompaniment)
have also been written. A few modern composers have applied
the term _concerto_ to certain large organ works (with no
orchestral accompaniment, the composition being written for
just the one instrument), but this use of the word is so
contrary to the accepted definition that it is hardly
justifiable.

When a concerto is played on two pianos (without orchestra),
this does not mean that there is no orchestral part, but that
there is no orchestra to play it, and so the parts that should
be played by the orchestral instruments have simply been
arranged for a second piano (sometimes organ).

156. A _symphony_ is a sonata for full orchestra. In general its
construction is the same as that of the sonata, but it is usually of
much larger proportions and has in it much greater variety of both tonal
and rhythmic material. The symphony is generally conceded to be the
highest type of instrumental music ever evolved.

The _symphony_ was accepted as a standard form in the time of
Haydn (1732-1809) and was developed enormously by Haydn
himself, Mozart (1756-1791), and Beethoven (1770-1827),
reaching perhaps its highest point in the famous "Nine
Symphonies" of the last-named composer. Later symphony writers
whose works are at present being performed include Schumann,
Tschaikowsky, and Dvo[vr]ak.

The word _symphony_ was formerly used synonymously with _ritornelle_,
both words being applied to instrumental interludes between parts of
vocal wor