I'm having trouble learning Moonlight Sonata without a piano teacher. What does a natural notation and a sharp symbol mean in front of the f, which is already sharp in the key signature?

  • 1
    Got a measure number? I'm checking. My guess is that it has something to do with a previous double sharp.
    – Josiah
    Jun 6, 2015 at 22:58
  • 2
    My guess is that it was an F## earlier in the measure and now it's an F# instead and the natural is to cancel the second sharp and the first is to remind you F's are still sharp.
    – Dom
    Jun 6, 2015 at 23:05

2 Answers 2


I can't find it in the edition I'm looking at, but probably this is a courtesy accidental to make it easier to remember what note you're playing.

Strictly speaking, courtesy accidentals aren't needed for any theory reason, but they can make a difference when playing. Usually they are found at the start of a measure canceling the accidental in the previous measure. They are up to the editor since they don't affect the playing of the music, and vary between editions.

In c♯ minor, fx is the leading tone to the dominant (g♯), so it occurs pretty frequently. To remind you when you're looking at a "regular" f♯ after a passage of fxs, you could see a natural and then a sharp.


It means that you are going from a double sharp to a sharp.

In classical notation for instance when you write a melodic minor scale with a double sharp going up and just a regular sharp going down you use a natural sign followed by a sharp to indicate the E## is going back to a E#.

  • I would add the word "Usually" to your first sentence. :-) Jun 7, 2015 at 12:14

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