I know you could just notate it as C or B natural, depending on the intention...

But theoretically, is this possible or is that confusing?

would it transform the note into B# (until the rest of the measure)? cancel out the original key leading to B natural? Or nothing because it is just not allowed/meaningless or too confusing?

  • It would simply change the key until the next measure cancels it out. There's a term for this... Let me find it... – General Nuisance Oct 17 '16 at 13:38
  • Ok, it's unclear to me if what you mean by "B#" is to raise the Bb note by a half a step (Bnat) or to make it a B#, because you seem to reference both in your question. – General Nuisance Oct 17 '16 at 13:40
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    This is a slightly confused question, as B# is enharmonically the same as C natural, but not B natural! – Tim Oct 17 '16 at 14:16

Accidentals have absolute power... Over a single measure. If you threw a B# in a key signature where the B is normally flat, it would change it to a B#. No questions asked. You can even change the key signature by using accidentals. This is called transposition... I think.

So if you wanted your Bb to become a Bnat, you would write Bnat into the measure as an accidental, or, as the case may be, change the key signature. But a sharp or flat does not change the pitch of the note relative to what it was before; it is played as written. If you see a B# in any key signature, you play a B#. End of story.

Hope this helps, and please ask questions should you have them or if my explanation is stupid.

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In F major, all Bs are played initially as Bb, and Cs as Cs. However,there could be a requirement to write a B#, for example, if there was a modulation using , say, E+. E augmented needs to have a B#, but not written as a C. Some folks would notate it as a C, which of course would sound the same, but technically it should be written as B#, which tells players who understand that the harmony containd an augmented 5th.

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It seems like you're asking whether the sharp "sharpens" a B flat to a B natural, or actually makes a B sharp. The answer is that, yes, a B# in F major would be the same enharmonic note as a C natural. So for the that bar, all written B's would be played as Cs, effectively.

The important question though is would this ever happen? And the answer is rarely if ever. You are raising the 4th degree of the scale by 2 semitones; to give you an analogy, all of the following are equivalent:

A B♯ in F major

An Fdouble sharp (double sharp) in C major

An E♯ in B♭ major

A C1 in G major

Which way we write a given note (for example B♭ or A♯) is called a "spelling". Why would we ever use these spellings?

  • Borrowing from C♯ minor, minor scales can have a sharp 7. This would be very unlikely in the key of F. (this would be like borrowing from G♯ minor in the key of C major)

  • Borrowing from C♯ major. Why would you do this when you could write it as D flat major, and have a C♮?

  • An E augmented chord has a raised fifth, not a flat sixth, so would be written as E G♯ B♯ (not E G# C). Quite why you would find this in a piece in F major though, I can't see. It would be like seeing an F♯ sharp augmented (F♯ A♯ C1) in the key of G... Why?

TL;DR B♯ would be a C♮. While it is technically possible to raise the fourth degree of a scale by 2 notes, there are few, if any circumstances where you would want to do this, and so you are unlikely to ever encounter a B♯ in F major.

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  • 'E aug has a raised fifth' - that's the same as a sharpened fifth, perfect + a semitone, isn't it? – Tim Oct 17 '16 at 19:48
  • yeah I meant to say not a flat 6, just a brain-typo I guess – Some_Guy Oct 17 '16 at 20:48

B# is B#, in any surroundings. It would persist until the next barline, like any accidental.

The likelihood of B# being a useful notation in an F major context is slim though.

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  • Oh it's extremely unlikely but great fun trying to justify. I don't think you read the latest edit of this post, missing the point perhaps? – RRR Dec 27 '16 at 10:34
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    You could certainly devise a justifiable reason for writing B# C# before a D minor chord, and that chord could obviously have a harmonic function in F major. – user19146 Dec 27 '16 at 11:12

This is a really fun if slightly useless question. Let's consider inder what REASONABLE circumstances a B# would appear in a piece starting off (because thats the ONLY thing a key signature means) in F Major. First let's look at which scales contain B# (that aren't unreasonably daft like for example D# Major):

C# Major

that's it for majors

and then non-daft Minor scales:

C# Minor Let's say Melodic
D# Minor Melodic
A# Minor ?

Now let's hunt for some (but not all) USEFUL chords properly containing B# when written correctly in the key:

(You know what, to hell with A# Minor.)

C# Major = C#Ma7 E#m7 G#7 B#m7b5 (=D#m6)
C# Minor Melodic = B# ALT, F#7b5
D# Minor Melodic = B#m7 b5

Can some of them be ruled out ? I would say so! E#m7 C#Ma7, B#m7b5, B# ALT, and B#7 b5 are revoltingly preposterous from a publishing point of view, even IF you are Charlie Parker.

But, HELLO! that leaves G#7 and you would probably spell that properly.

There you go! Now we'll just figure out a pretty progression and ...

F Ma7 | F Ma7 b5 | A Ma7 | G# Ma7 b5 | G Sus Ma7 | F# Ma7 b5 | F Ma7 |

Yeah, ok so I changed it. And I know G# Ma7 b5 is in D# Major after all. Daft key. Play all these in Root inversion. Here's how it works. You're not going to spell the A Ma7 with an A Flat are you, so you're going to spell the next chord properly, G#, B#, D, FX. After that the B# is PEDALLED thru all the chords, SO YOU CAN'T CHANGE IT, even the final FMa7 ends up being spelled with a B#! If I ever figure out how to score it on a staff on this site, I will. Till then use your imaginations.

So, I don't know what was the question? Oh yeah IF you ever saw a B# it might be in a progression somefink like the one above.


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