Hi,

Long time since we first learnt what were ♭ and ♯ ... See this post for details !

Today, we'll discover 2 more accidentals :

  • double sharp : 𝄪
  • double flat : 𝄫

Their use is mainly related to minor keys1 or diminished chords2. We'll talk about that in their respective posts.

The double sharp (𝄪) raises a note one whole step, and looks like a cross Here is an example using double sharps.

The first measures show a double sharp in a melodic context, whereas the last measures show how double sharps behave. (a double sharp cancel all previous accidentals, and is cancelled by any accidentals)
Note that a 𝄪F sounds like a G. We'll see in the minor scales post why sometimes it is more convenient to write 𝄪F instead of G.

The double flat (𝄫) lowers a note by a whole step, and looks like two flats glued together. Here is an example using double flats.

Note that, like double sharp, or any accidentals, a double flat cancel all previous accidentals, and is cancelled by any accidentals.
Besides, 𝄫B sounds like a A. We'll see in the diminished seventh chord post why sometimes it is more convenient to write 𝄫B instead of A.

That's all for today :)

Have a good day
Sebastien

  1. As in this score,

  2. As in this score,