It is a great fallacy to think that it is more difficult to play passages and intricate ornamentation in music very fast, or very loud, than softly and at a moderate speed. It is often the contrary which is the case. Pianists sometimes increase their tone and their tempo more than they intend to do through nervousness and want of confidence or from fear of failure of memory.
How to play difficult passages : piano ornamentations
The pianist who can play a long series of intricate and more or less rapid successions of passages in a slow tempo, and pianissimo, with a lot of rhythm, is often doing thereby something that is actually harder to achieve than the more showy splash-dash which to the uninitiated might seem most wonderful. Of course the greatest technique implies absolute mastery and judgment in everything, so that the brilliant fast passage is given with the necessary force and lean, while the soft elegant ornamentation receives in its turn grace and finish.
Finger articulation : play rhythmically
To play rhythmically the pianist must possess technique of finger articulation, to play with color he must acquire the technique of the pedal, to play with feeling and emotion he must have the technique of touch, to play with power he must learn the technique of how to apply strength.All these many branches go to make up the one comprehensive material called technique which the pianist must work with to produce his aesthetic objective. Therefore no student may despise or undervalue even its most mechanical aspects. For as in architecture every humble and uninteresting stone has its own indispensable aesthetic necessity in the building of the palace or cathedral, even so is it also in pianoforte playing; to attain the noblest results no details of workmanship, however insignificant, should be neglected. Genius means not only imagination and temperament, but also the capacity of conveying them to the world through the vehicle of some medium, over which a complete mastery has been obtained.