I've been playing piano by ear for a long time and now I am trying to learn the first movement of the Moonlight Sonata. I am a little confused about the meaning of a little cross placed right before a note.

It seems to cancel a sharp or something, but the meaning is not quite clear! If you understand the symbol I'm describing help me out here!


3 Answers 3


I'm assuming that you're talking about the one that looks like a blocky X.....this is a double sharp. Instead of shifting the tone up one half step, it shifts the tone up 2 half steps (i.e. 1 whole step).

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This image shows G double-sharp in the treble clef, and E double-flat in the bass clef. G double sharp is enharmonic with A natural, and E double-flat is enharmonic with D natural.

Coincidentally, Moonlight Sonata is the piece where I first encountered double-sharps, too!

  • 2
    I think what brought confusion while I read was that at some point I think there was a double sharp on a note which was already "sharpened" in the scale, is it possible that in this case it only "raises half a tone"? If you understand what I mean. Commented Mar 25, 2012 at 3:59
  • 13
    Yes; this overrides any other accidentals in the key signature. Think of it as sharping a sharp, if it helps. For a more thorough discussion than I can provide, you should look at this question. music.stackexchange.com/questions/87/…
    – Babu
    Commented Mar 25, 2012 at 14:55
  • @PatrickDaSilva: Like you noticed, it really raises it half a note from the already sharpened note in the key signature. This is the most common situation to use the double-sharp. I have never seen it used to raise a note a whole step that is not already raised by a normal sharp. See the linked question in Babu's comment for more details on why it is used.
    – awe
    Commented Mar 30, 2012 at 11:03
  • 2
    @PatrickDaSilva All accidentals "cancel" whatever was in place before; adding a sharp to a note that's already sharped in the key signature is equivalent to "reminding" the player that this note should be sharp, not adding an additional sharp. Similarly, adding a flat would lower it two half-steps from the "sharp" version of the note, not bring it back to a natural. Commented Jun 1, 2013 at 21:12
  • 4
    Probably the most commonly encountered double-sharp is Fx in a piece in c#-minor, so I'm not surprised you both encountered it for the first time in what is probably the most famous c#-minor piece. This is because modulating to the dominant key is so common, and the key of G# needs a leading tone. Bach invented the symbol for one of the C# pieces in the Well-Tempered Clavier. Commented Jun 20, 2014 at 23:15

Babu's answer contains the canonical answer, it is a double sharp used to sharpen a note that already had a sharp applied.

I can see how it is hard to find these things, when we see the symbol on the page what on earth would we type into a search engine? This is where visual lists of musical symbols come in useful. Wikipedia provides one such list of musical symbols which we can visually scan to find the symbol we are looking for. Yours is about halfway down the list:

Wikipedia screenshot

  • Of significance is that the raising is not cumulative? So if it is already a sharp because of a key signature this does not mean 3 half tones? It means one more. If we were coming up with this today we might have used an up arrow or a "+". Almost grammatical.
    – mckenzm
    Commented Nov 20, 2023 at 4:11
  • @mckenzm neither accidentals nor key signature is cumulative. They always replace whatever would apply to the given note before. See music.stackexchange.com/questions/24355 Commented Nov 20, 2023 at 17:13

I believe the X before a note means you play a double sharp. This, in C Major key, if it is placed before b note,one half tone up takes the note to C. But you need to play an extra sharp (or half tone up), so you'd play C# because the Major scale pattern is: Tone,Tone, Tone, Semi Tone, Tone, Tone, Semi tone, tone (adding up to 8 notes of this scale). The semi tones for C Major scale will occur between E and F intervals and the B and C intervals of the scale. In a different key's scale, the Major key intervals would follow the same pattern but would, obviously, occur between different note names, because your tonic or starting note of the scale will be different.You need to be aware of how scales are constructed to know which note to hit when you see a double flat or double sharp sign on the notation. You can't simply play the next letter name up or down because, depending on the key you're in, this may result in some pretty unpleasant dissonant notes. Though some experimental musicians may like exploring the creative possibilities of such off sounding wrong notes.Ever struggled with learning a hard classical piece, hitting the wrong notes and then thinking: Hey I quite rather like that "new sound", even though I know it's wrong, not what the composer wanted played.

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