material in another. His fifth and last pianoforte concerto, in E flat,
commonly called the "Emperor," begins with a rhapsodical introduction of
extreme brilliance for the solo player, followed by a tutti of unusual
length which is confined to the tonic major and minor with a strictness
explained by the gorgeous modulations with which the solo subsequently
treats the second subject. In this concerto Beethoven also dispenses
with the only really conventional feature of the form, namely, the
_cadenza_, a custom elaborated from the operatic aria, in which the
singer was allowed to extemporize a flourish on a pause near the end. A
similar pause was made in the final ritornello of a concerto, and the
soloist was supposed to extemporize what should be equivalent to a
symphonic coda, with results which could not but be deplorable unless
the player (or cadenza writer) were either the composer himself, or
capable of entering into his intentions, like Joachim, who has written
the finest extant cadenza of classical violin concertos.

Brahms's first concerto in D minor, _Op. 15_, was the result of an
immense amount of work, and, though on a mass of material originally
intended for a symphony, was nevertheless so perfectly assimilated into
the true concerto form that in his next essay, the violin concerto, _Op.
77_, he had no more to learn, and was free to make true innovations. He
succeeds in presenting the contrasts even of remote keys so immediately
that they are serviceable in the opening tutti and give the form a wider
range in definitely functional key than any other instrumental music.
Thus in the opening tutti of the D minor concerto the second subject is
announced in B flat minor. In the B flat pianoforte concerto, _Op. 83_,
it appears in D minor, and in the double concerto, _Op. 102_, for violin
and violoncello in A minor it appears in F major. In none of these cases
is it in the key in which the solo develops it, and it is reached with
a directness sharply contrasted with the symphonic deliberation with
which it is approached in the solo. In the violin concerto, _Op. 77_,
Brahms develops a counterplot in the opposition between solo and
orchestra, inasmuch as after the solo has worked out its second subject
the orchestra bursts in, not with the opening ritornello, but with its
own version of the material with which the solo originally entered. In
other words we have now not only the development by the solo of material
state