Knowing the subject and any countersubjects within the fugue and identifying them thourghout the piece is also valuable. If you play the subject one way, you must stick with it throughout - do not change the phrasing because if you do, the familiarity of it will dissappear and due to the complex nature of a fugue it will be difficult to re-establish a sense of comprehension.Episodes within the fugue, parts of the fugue where there are no subjects should still follow familiarity. Usually in a Bach fugue, there are episodes that repeat. These episodes should be played in a similar manner because it establishes familiarity.
Even if the subjects and counterpoints are played in a different manner each time it is played, I dont think that the familiarity is lost... No matter how Bach is played, voices are clearly identifiable.- Monika