Krapp’s Last Tape, which works extremely well in performance, is quite difficult to read, to stage in the mind’s eye, because there are two Presents here – the actual present that is shared with the audience, when he is listening and recording, and the present time of the tape he is listening to, which can be anytime in his past.  The reader must pay careful attention to the information in the "stage directions."

    The clearest, most obvious use of light and dark is in what I will call the “Performance Present”; Beckett gives Krapp a dark upstage place to go in the Performance present to represent the rest of Krapp’s world – he goes there to drink, to get a dictionary, etc. – any activity not directly germane to the tape listening and recording.  In the “Biography Present” some events occur in daylight and some in the dark, but can be seen as part of the details of the mise-en-scene of Krapp’s past.  Along with season references (Autumn, etc.), they can reflect the waning of his life as the tapes are replayed and the memories (presumably) recalled.  Bridging the two Presents are such devices as the song:

 Now the day is over,
Night is drawing nigh-igh,
Shadows—

 And the remark:

Past midnight. Never knew such silence. The earth might be uninhabited.

The contrasts of light and dark also serve as universal symbols: understanding and ignorance; good and evil, youth and age, etc.

But, as usual with Beckett, one cannot assume psychological characterization.  It is also interesting to note that once again Beckett use a pair of characters (the present Krapp and the Krapp on tape.)