The charm of improvisation lies, of course, in this, that we hear a
composer creating and playing at the same time. This very fact,
however, ought to make us cautious not to overestimate the value of
such improvisations. For we all know how a great genius can invest
even a commonplace idea with charm by his manner of expressing or
rendering it. It is probable, therefore, that in most cases these
improvisations, if noted down and played by _others_, would not make
as deep an impression as the regularly written compositions of the
great masters. It is with music as with literature. Schopenhauer says
that there are three classes of writers: The first class, which is
very numerous, never think at all, but simply reproduce echoes of what
they have read in books. The second class, somewhat less numerous,
think only while they are writing. But the third class, which is very
small, only write _after_ thinking and because their thoughts clamor
for utterance.

If we apply this classification to music we see at once that
improvising comes under the second head: improvising is thinking or
composing while playing. But the greatest musical ideas are those
which are conceived entirely in the mind, which needs no pen or piano
mechanically to stimulate its creative power. Of this there can be no
question, whatever. With an almost absolute unanimity we find that the
greatest composers conceived their immortal ideas in the open air,
where there was no possibility of coaxing them out of an instrument.
And not only is the bare outline thus composed mentally, but the whole
composition with all its involved harmonies and varied orchestral
colors is present in the composer's mind before he puts it down on
paper. The composition of "Der Freischütz" affords a remarkable
confirmation of this statement. Weber began to compose this opera
mentally on February 23, but did not write down a single note before