In order to learn a piece of music fast, we need to be aware of the following 3 steps:
First– analyse the piece of music and make sure that you understand all of the elements (melody, rhythm, harmony, counterpoint and form) along with the technical considerations that are instrument specific.
Secondly– play at a tempo that gives you complete control over everything; develop the ability to look ahead- anticipating each note and the resulting hand movements to play them accurately. Remember that control comes from constant listening and evaluation.
Thirdly, do not play through the entire piece of music, but break it down into smaller chunks, making sure that each section is not too long in duration. The length of these sections is determined by your own musical capabilities, so the lower level of musical and technical development, the shorter each section should be.
So to recap, if the entire musical blueprint is too difficult to process at once, make sure to isolate separate parts and work them out before putting all together again. This could apply to the harmonic structure, the rhythm, melodic design, phrasing, dynamics, articulation, compositional form, hand positions as well as fingering problems. After perceiving all of these logical connections that serve to unite the music, this approach will help you to understand how the music should sound at faster tempos and enable you to play as fast as needed when required.
All the Bass!