Here, I’ll ask a dumb question. Then people can tell me there are no dumb questions.
I just had an existential crises in the music theory course. Secure in my knowledge that there are no sharps between B and C, and E and F, Just was just talking about how there are 7 sharps in the C# Major scale.
That would require the scale to look like this:
C♯, D♯, E♯, F♯, G♯, A♯, and B♯
I thought there was no such thing as B# or E#?
Help please, and thanks for your patience, in advance.
Hi Brian @Jingledale , I’m working through the theory course, albeit slowly, as well. This stumped me at first. I found two concepts to sort this out. First, there is a semitone between B and C, E and F. Second, a note can only appear one time in a scale.
The major scale formula is tone - tone - semitone - tone - tone - tone - semitone.
Starting at C#:
C# - D# - (F) - F# - G# - A# - (C)
This is a problem - two versions of F, two version of C!
So we replace that F with E#, and the C with B#.
It’s easier to see if you look at the note circle. I’m sure someone will provide a more theory-based explanation, but this is how I remember it!
B# is enharmonically equivalent to C, and E# is enharmonically equivalent to F - meaning that they sound the same, but are “spelled” differently (just as Eb and D# are the same note “spelled” differently). They end up “spelled” this way in some key signatures because, as Judi said, each note (letter) can only be used one time in a scale.
Editing to add that this is 100% not a dumb question - it’s a tricky little detail!
There isn’t per say (IE:no black key), BUT. ! you can Sharp, Flat, double sharp or double flat, or naturalise any note in a piece of music.
Natural note means remove it’s sharp or flat.
To answer this correctly you’ll need the man @Richard_close2u to see this 
|Major key|Number of sharps|Sharp notes|Minor key|Enharmonic equivalent|
|C major|0|–|A minor|None|
|G major|1|F♯|E minor|None|
|D major|2|F♯, C♯|B minor|None|
|A major|3|F♯, C♯, G♯|F♯ minor|None|
|E major|4|F♯, C♯, G♯, D♯|C♯ minor|None|
|B major|5|F♯, C♯, G♯, D♯, A♯|G♯ minor|C♭ major/A♭ minor|
|F♯ major|6|F♯, C♯, G♯, D♯, A♯, E♯|D♯ minor|G♭ major/E♭ minor|
|C♯ major|7|F♯, C♯, G♯, D♯, A♯, E♯, B♯|A♯ minor|D♭ major/B♭ minor|
R.
Brian - no stupid questions!
This needs a minor but very important correction.
There are no NOTES / TONES (in western music) between B and C then E and F respectively.
All four of those notes can be natural (B, C, E, F), sharp (B#, C#, E#, F#) or flat (Bb, Cb, Eb, Fb).
B# = C (enharmonic equivalent notes given different names depending on the context).
E# = F (enharmonic equivalent notes given different names depending on the context).
Cb = B (enharmonic equivalent notes given different names depending on the context).
Fb = E (enharmonic equivalent notes given different names depending on the context).
The reason for their existence is …
a] When spelling a major scale all seven letters must be used once and once only.
b] a key with one or more sharps can only contain natural or sharp notes (no flats allowed).
c] A key with one or more flat notes can only contain natural or flat notes (no sharps allowed).
Examples of each.
a]
C major using all seven letters once and once only.
C, D, E, F, G, A, B
b]
A major (using sharps and natural notes only)
A, B, C#, D, E, F#, G#
c]
Eb major (using flats and natural notes only)
Eb, F, G, Ab, Bb, C, D
So far so good I hope and none of those examples use the ‘oddities’ you ask about.
When do the oddities become necessary?
B# (= C) is needed if a major scale has already use the letter C. The letter C being used cannot be the natural note C as, just as we cannot use a letter twice nor can we use the same tone twice. If B# is needed it will be due to the fact that C# appears in the scale. If the letter C has already been used, and B follows along later, it must be that we started at letter C, the position of the 1st scale degree, and the letter B is found at the position of the 7th scale degree. There is only one scale that fits the bill, namely C#.
C#, D#, E#, F#, G#, A#, B#
E# is needed if a major scale has already use the letter F. The letter F being used cannot be the natural note F as, just as we cannot use a letter twice nor can we use the same tone twice. If E# is needed it will be due to the fact that F# appears in the scale. If the letter F has already been used, and E follows along later, it must be that we started at F, the position of the 1st scale degree, and the letter E is found at the position of the 7th scale degree. There is only one scale that fits the bill, namely F#.
F#, G#, A#, B, C#, D#, E#
Cb is needed for the Cb major scale (of course it is).
Cb, Db, Eb, Fb, Gb, Ab, Bb
Fb is needed (as shown directly above) in the Cb major scale and in no other major scale unless you venture into the world of double flats. This matches with the order of flats - the note F is the last of seven to take a flat. See Mr Cato’s trick.
Thanks to the people who replied to my question AND let me know know there are now dumb questions.
I think I’m rounding the corner on this one. There are 2 things I learned since last night when I posted my question, that have helped me understand how B# and E# would appear in the scale.
1.) When writing out the C# Major scale, I need to note (no pun intended) that it’s scale of sharps, therefore, it’s legit to use the two “fake” sharps of B# and E# because you can’t use and flats.
2.) This point has been made by several helpful people. You can’t repeat a letter in a scale. So, you can’t write C and C#, for example, you would have to write C and Db.
Again, thank you all and I hope I pass the audition.
You just set me free with these three lines:
a] When spelling a major scale all seven letters must be used once and once only.
b] a key with one or more sharps can only contain natural or sharp notes (no flats allowed).
c] A key with one or more flat notes can only contain natural or flat notes (no sharps allowed).
I sort of figured some of this out last night but you put it very succinctly.
Thank you!
Thank you, Judi!
Thank you for responding. You’re right, it is a tricky question for theory beginners. They start you off with the absolute rule, “There’s no semitone between B-C or E-F!!!” You commit that to memory and then, it doesn’t work when writing the C# Major scale. It’s not intuitive, but I believe I understand it now.
Thank you for replying. And, you were right, I needed Richard the man.
He gave me a lot of info but these three lines really cleared it up for me.
a] When spelling a major scale all seven letters must be used once and once only.
b] a key with one or more sharps can only contain natural or sharp notes (no flats allowed).
c] A key with one or more flat notes can only contain natural or flat notes (no sharps allowed).
Great answer
My teachers always used to shout this at me 
Is that because you kept asking stupid questions!
Yes, I’ve discovered that. I’m at the point now, in the music theory course, where I’m alternately wondering why I should continue AND starting to understand some of it — like, why a 3 chord blues song is called a 1,IV, V progression.
Yes, my teachers shouted, “There are no stupid questions!” at me too…but the smirk on their faces, when I asked the question, and the laughter of fellow students, taught me that they didn’t really mean it. < : o ( <–Me in my dunce cap
didn’t read the thread, but chiming in as it seems the title summoned me 
