Here is a new way to look at understanding human memory: the memory unit. I consider the basic functional memory unit to be the amount of material which can be played or studied six times and then played by memory the seventh.
This is based upon the limitations of the short term memory. These limitations are 10 – 15 seconds and 5 – 7 “chunks”. A chunk is a single idea which can be made of many individual bits of information. A one octave C major scale can be looked at as either 8 chunks, where each note requires a new idea. Or a single chunk, the entire scale being conceived as a single idea which contains all of the note and fingering information.
The short term memory only lasts about 10 – 15 seconds before information is dumped. If the memory is re-heard (read: rehearsal) within this time limitation and the content can begin to be moved intact into the long term memory.
This is a critical point. I once had a student tell me that they always got lost in a particular passage in the middle of a rather long phrase. They had attempted to memorize this passage working in sections which exceeded the capacity of their short term memory and the information was not moved intact to the long term memory. They simply had no idea of what was in the middle of the phrase.
I know this sounds rather technical and mechanical, however, our brains are chemical machines and consequently do have a predictable pattern of behavior at a certain level. Try this experiment: Select one measure of music, play it 6 times, close the music and play it again. If you are successful, you stayed within the contents of the short term memory. If not, either you played really slow, taking longer than 15 seconds, or didn’t group the notes into any chunk or pattern. Next expand to a two measure passage, and then three and four measures. At some point you will reach your limit; that is your memory unit.