Can any one please explain what is an accidental note? Do they have any rules to play accidental notes in a scale? I only have basic knowledge of keyboards.

5 Answers 5


To understand what an accidental is, you must first understand what a key signature is.

That is answered at: What is a key signature?

.. but briefly, a key signature is a set of markings telling you which notes to always play as sharps or flats. For example, the key signature for F major consists of a ♭ in the B position, meaning "Whenever a B appears in this score, play B♭".

An accidental points out a note which is an exception to the key signature. It is a note with a ♯, ♮, ♭ next to it, to say "although the key signature says otherwise, for this bar only, play it like this".

  • Isn't it also worth mentioning that a well-trained musician can sometimes spot an accidental because it sounds slightly "off"? (of course some music genres use a lot of accidentals by definition, like the blue note in blues)
    – mkorman
    Jan 14, 2021 at 16:45

Accidentals are notes which don't usually occur in the key the piece of music is in.

For instance, if you're playing a piece in C major and there's a B flat, then this is an accidental note since B flat isn't in the scale of C major.

Accidentals are easy to spot in notation since they'll always have a sharp ♯, natural ♮, or flat ♭ sign in front of them.

  • 4
    yes, also, dont think that because its an accidental it means that its an accident. they are very deliberate Apr 18, 2013 at 13:33
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    While this is splitting hairs, accidental notes are notes which don't occur in the key signature of the piece, not specifically the key... Tchaikovsky is a great example of how just because a section is in a certain key signature does not mean that it is in that key the whole time!
    – margalo
    Nov 2, 2016 at 3:26

In the key of C, the "accidental" notes are the black keys on your piano.

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In any other key, the "accidental" notes are whatever notes that you need to play in the piece which are not in the key itself, and thus not in the key signature.

  • A thought : in C maj.,e.g., a bar needs an F#.So an accidental # is written in front of the F. In the same bar,after this, an F natural is needed. So a natural sign is put before the second F.Surely then, the natural sign is still called an accidental, thus in your example, a white F natural can also be an "accidental" note, even in its own key.
    – Tim
    Apr 18, 2013 at 15:37
  • @Tim Don't confuse the symbol and the note. The natural sign is an accidental, but a note that is part of the key is not an accidental note regardless of whether it is prefixed with an accidental.
    – user28
    Apr 18, 2013 at 16:10

Don't forget also the (x) and the (bb). Double sharps and double flats occasionally need to be used, to sharpen an already sharp (as in the written key signature) note, and vice versa.E.g. in Db, there is already a Bb in the key sig.If one wanted to write a chord of Gbm; the third, normally a Bb, would need to be flattened again.Thus it is written as Bbb or B double flat.Yes I know lots of guitarists in particular would call it an A !!! But technically it must be called a B note of some sort - hence Bbb. These, I suppose, are actually the only accidentals that never get used as anything else.

Also, don't forget that after the next bar line following an accidental, all accidentals from the previous bar are cancelled.It really bugs me that so many pieces of music put the cancelling natural, for example, in the next bar.Totally pointless, yet seen in lots of piano exam pieces, especially at lower grades. All it does is add extra superfluous marks to distract the player.

  • You're right that the cancelling natural isn't necessary, but many scores include them for clarification so there's no ambiguity about whether the note is natural or not. This also occurs on accidentals in different octaves in the same bar - if a C in one octave is sharpened, then there's usually a natural sign on a C in another octave to clarify what the composer means. Apr 19, 2013 at 8:47

The twelve tones in any chromatic scale are divided into two groups: Solfeggio and Accidental

In the Key of C, do-re-me-fa-so-la-te (called solfeggio) are played on the white keys, where as di-ri-fi-si and li (called accidentals) are played on the black keys

The entire tonal chromatic scale is: do-di-re-ri-me-fa-fi-so-si-la-li-te

In the Key of C the accidentals are C# - D# - F# - G# - A#

Solfeggio form the roots of "Natural Chords" represented by Roman Numerals I-ii-iii-IV-V-vi-vii

Accidentals form the roots of the "Flatted Chords"
flatted II, flatted III, flatted V, flatted VI and flatted VII (all played as major triads as the roman numerals are all capitals)

Thus all 15 Chromatic Scales have the same tonal labels, which makes transposing from the Key of A (easiest for guitarist) to the Key of C (easiest for the pianist) extremely easy. Instead of thinking A is transposed to C, think: A is a 1 in the key of A and C is a 1 in the key of C. That is why learning tonal scales and their corresponding roman numeral labels is a must for writing and transposing.

I'm a self-taught song writer and have spent many years searching through music theory books and talking to professionals. I have talked to many piano teachers who have had no clue that the accidentals have tonal names, nor do they understand the need for Roman Numeral designations. "What's the Circle of Fifths?" is a favorite common response I get from piano teachers. I guess if you only want to read sheet music, there is no need for music theory, but it has helped me fully understand what I truly love: music!

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