I am trying to learn the piano and I am a bit confused when it comes how sharp notes are represented in the sheet.

I am working my way through Prelude I in C Major (BWV 846), and in the sixth bar/measure my sheet looks like this

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(Sheet from musescore.com)

To me, that looks like I am supposed to play

F# A D F A D F A D F A D

but I think it's actually supposed to be this

F# A D F# A D F# A D F# A D

Am I playing it right by playing it as all the Fs being sharp, and if so, how can I tell from the sheet that they are sharp if only the first one has the #?

  • 3
    You say that it is C major, which has no sharp or flats. If the sharp or flat sign is directly before a note, only this pitch should be transposed until the end of the bar. This sign does not affect other octaves. If the sharp or flat signs at part of the key signature, however, they are valid for the whole piece and also for every octave. So, in this case: yes, this sign affects all the Fs at this octave in this bar. Commented Aug 28, 2020 at 8:47
  • 3
    You're correct, and it would seem that your ears have given you good guidance!
    – Tim
    Commented Aug 28, 2020 at 8:53

3 Answers 3


This F# is what one would call an accidental: it is a sharp (or a flat, or a natural) which is not part of the key signature.

The rule is: when an accidental is printed, it applies until the end of the current bar (and only to the octave where it appears). Meaning your second version is correct.

There are numerous questions about this here, feel free to add references to a more complete explanation to this post.

  • Thank you, @Tom! What if the music is supposed to be F# F in the same bar, what would the notation look like to show me that the second F is not affected by the first #?
    – bornander
    Commented Aug 28, 2020 at 8:57
  • 2
    @bornander In that case you would have a natural accidental in front of the second F. Note that it also applies when you are in a key signature which naturally contains flats or sharps. I'll add the natural to my list!
    – Tom
    Commented Aug 28, 2020 at 8:59
  • 1
    Accidentals only apply to the octave, where they appear, however, see this question.
    – guidot
    Commented Aug 28, 2020 at 12:51
  • 1
    @guidot yes, good precision!
    – Tom
    Commented Aug 28, 2020 at 14:01

When a sharp is accidental in a major scale, such as C, the sharp is consistent until the new bar measure. So you would play F# until the new bar measure. Hope this helps;)

Kenny, pianist

  • 1
    What difference with the answer already posted?
    – Tom
    Commented Aug 29, 2020 at 7:37

Mastering and accepting this basic rudiment is important but of even more importance is learning to recognize, at a glance, the "harmonic implication" of a group of notes. In other words, what is the chord that is suggested by these notes and what is the harmonic function of that chord? Too many otherwise well trained musicians think from note to note rather than what the chord, or harmonic structure of the music is. In this case, if a "pitch inventory" of the given is made, it clearly spells out an inversion of a D7 chord with the 7th as the lowest note. The next question to be answered is what is the fuction of a D7 chord in the key of C major? Well, it is a "secondary dominant" that is "tonicizing" the G or dominant chord in C major. Think always about chords as opposed to one note to the next.

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