B# and Cb octaves: bug or feature?

• Jun 15, 2019 - 09:58

OS: macOS Mojave (10.14)
Arch.: x86_64
MuseScore version (64-bit):
revision: e26f7c4

I've seen some messages in the past about incorrect export in musicXML, like this

Now, I noticed that now despite the B# and Cb notes play correctly, the note names still change the octave
A flatted C5 becomes a Cb4 and a sharpened B4 becomes B#5...
Is that the expected behaviour? Does the octave name relate only to the note frequency?
I supposed that a B4 or C4 would remain named as such, only with the alteration added.

This things reflects in the musicXML esported file, and I noticed that while writing a javascript parser...
Should I adapt my routine to this behaviour or is it a bug?

I don't have access to other notation programs at the moment so I cannot check what Finale, Sibelius, etc... do.
thank you

Attachment Size
B.png 69.81 KB
B#.png 71.07 KB
C.png 72.66 KB
Cb.png 71.05 KB


In reply to by Jojo-Schmitz

no need actually,
just open a new blank score, and manually insert a B (e.g. a B3, third row), notice the name in the status bar, then add a sharp (or a flat, if you inserted a C), and notice the octave change...
I attached the 4 screenshots in my message...

Good dilemma. I think changing octave names is the correct way to do this, because the octaves are defined by where they are on the keyboard, not their names. When you press the B# key you are actually pressing the C key. So the jump up an octave for a B# is what I would expect. The same logic works for Cb.

In reply to by mike320

It makes sense from a mechanical keyboard perspective, but isn't it a 'hiccup' when it comes to musical analysis/parsing?
If I see a B3 that becomes a B4 (moreover sharpened, B#4...) I think to a b9 interval...
I wonder if they will have this topic discussed for the next MIDI standard version definition...
Anyway, I temporarily adapted my routine, since I cannot change Musescore behaviour...
I Wonder what other people think, and how other notation programs go...

This is not a matter of taste or what you think or I think. This has to be defined somewhere in some standard and there must be an absolute answer.

C-flat and B-sharp issues

There is some possible confusion regarding the assignment of an octave to C♭ or B♯. The convention is that the letter name is first combined with the Arabic numeral to determine a specific pitch, which is then altered by applying accidentals. For example, the symbol C♭4 means "the pitch one chromatic step below the pitch C4" and not "the pitch-class C♭ in octave 4", so C♭4 is the same pitch as B3, not B4. Similarly, at the other end of the fourth octave, B♯4 is the same pitch as C5, not C4.

The matter may be clarified by viewing "♭" and "♯" as denoting lowering or raising by a variable amount. In equal temperament, that amount is exactly 21/12 ≈ 1.0594631, or 100 cents, whereas in quarter-comma meantone it is precisely 57/4/16 ≈ 1.0449067, or 76.049 cents, taking other values for other meantone tunings. Hence "C♭4" is the same as "C4♭", which in equal temperament is 100 cents below middle C, and equal to B3. In quarter-comma meantone, C♭4 is 76.049 cents below C4 and 41.059 cents (ratio 128/125 = 1.024) sharper than B3, which is 117.108 cents (ratio 8/55/4 = 57/4/15.625 ≈ 1.0699845) below C4.

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