The double natural is a theoretical accidental symbol that is not used in common practice. The double natural is an accidental symbol that completely cancels the effects of a double sharp or double flat symbol. The double natural consists of two natural signs to the left of the note to be altered. As with all accidental symbols, this only effects the notes with that exact pitch in the same measure.
The double natural symbol cancelling a double sharp will lower the pitch of the double sharp by one full step (two semitones) and the double natural symbol canceling a double flat will raise the pitch of the double flat by one full step (two semitones). As mentioned above, the double natural symbols are not typically used in common practice, but would only used in highly chromatic passages (passages with lots of accidentals).
In practice there is no functional difference between a double natural symbol and a regular (single) natural symbol as both symbols cancel any prior alteration of the pitch. In the example below, the first column shows the written pitch C (C5) with a double sharp in the top row and a double flat in the bottom row. The second column shows the written pitch C (C5) with a double natural symbol that cancels out both sharps and both flats. The third column shows the recommended notation for canceling the double sharp and double flat. It is more useful to avoid the use the double natural notation and use the more conventional and recommended notation shown on the third column.
Last Updated: 2013-02-25 20:01:01