Yes, I think we're on the right track here. The E# is a logical result from using the
Circle of Fifths as means to establish a key. Notes that are notated differently but would actually "sound" the same (not sure about this fretless stuff stratwrassler mentioned) are called
enharmonic.
*** Little note to Stratwrassler: Cb and B# are NOT enharmonic. Cb would be enharmonic to B, while B# would be enharmonic to C. Same holds true for E# and Fb. ***
You can look at this basic
Major Key explanation here to see the same key signatures as displayed in the Circle of Fifths. Note that the way they are arranged follows the Circle of Fifths and the number of sharps/flats used. There is a certain pattern in which the sharps and flats are assigned. This "trick" can be a great help in dealing with standard notation (and perhaps key signature theory in general)
As you can see, E# is represented in the key of F#, which is actually a more common key than you would think. Strictly speaking, every key further clockwise along the circle would contain E# as well, so Kirk was actually right when he mentioned the key of A# (Note that it's more common enharmonic counterpart is the key of Bb). However, if you extrapolate a little and think about it, the key of A# would contain 10 sharps(!) and that means that certain notes will receive a ## (also notated as
X). I think I should stop here, lest I confuse you more than I'd enlighten you
Hope I've shed some light on the subject. Good luck!
