There are some absolutely wonderful piano pieces that are meant to be played fast but it can be completely daunting to attempt to play a fast piece of music. So how do you go about learning something that is so fast? The answer to that is slowly.
It might appear that my answer makes no sense at all, but let me assure you that in order to play a fast piece of music , you have to take your time and learn it slowly. The reason why you should always start slow is because when playing and learning something new you need time to think. You need to think about what notes you are playing and where the rests are . You also need to consider the timing and whether your crochets (quarter notes), quavers (eighth notes) and minims (half notes)for example are in the correct proportions in relation to each other. It doesn’t matter what note values you have, they all need to be in proportion with all the other notes. For example, no matter what your speed is, a semibreve (whole note) should always be precisely four times longer than a crochet (quarter note).
The best way to learn a fast piece of music is to learn the notes, the timing and the fingering first. Get all three of these components learned really, really well. It does not matter how slow you go to get your notes, timing and fingering learned. The most important thing is accuracy, not speed at this stage. The more proficient and familiar that you become with the music, you will find that you naturally start getting more speed without even trying to go faster. What you need to make sure that you are not doing is getting faster in sections. While this might seem that getting faster in sections will help you get the whole piece of music faster, experience has shown me that this is a hindrance because you need to have the whole thing at the one consistent speed. It is much easier and more efficient to speed the whole piece up gradually, once every other component is thoroughly known, than having sections at differing speeds.
Once you know the notes, timing and fingering very well, you will probably be able to play most of the piece of music from memory. It doesn’t mean that you need to try and memorize the music, but memorization usually comes with familiarization without really trying. Another aspect of knowing a piece of music really thoroughly is that you develop muscle memory, which means that your fingers and hands will know where to go and which notes to play because it has done it so many times beforehand. Once you have muscle memory of a piece of music, then learning to play the piece of music at a fast tempo is actually a fairly quick process. The way to go about it is that you just push the speed a little faster and practice it at that speed until it becomes comfortable to you, then you push the speed a little more. Repeat this process until you can comfortably play the whole piece of music full speed.
Learning to play a fast piece of music can be a bit of a challenge, but following the above process will ensure that with time and effort, you will be successful.