If I have a flat for a note in the key signature, and then in a bar the same note with an flat symbol, does that mean the note is "double flatted"?

For example in the key of D Minor with hash one flat (B♭): This means that all B's are actually B♭'s. But if I have a B♭ in a bar , does that mean it's actually B♭♭ (A)?

Another example:

enter image description here

Here it is the third note that has a flat by itself as well as in the key signature.

  • What would be the point in putting that Eb accidental ?
    – Tim
    Commented Jul 1, 2021 at 11:05
  • In the image above, the E has a flat accidental to hammer home that it's the flat 9 of the accompanying D(b9) chord. Commented Jul 5, 2023 at 11:58

6 Answers 6


No, it is still a B♭ as the accidentals in the key signature and measure are never additive. The flat is just reminding you that the B is flat. This is known as a courtesy accidental and is typically done if the previous measure uses a B that was different then the one in the key signature or if there was a different quality of B used in the measure it is used to cancel out the other quality.

In the key D minor, if you were ascending from A to D, a typical melody would be A, B, C♯, D. If you were descending in the next measure back to A, your melody would be D, C, B♭, A. It would be typical to remind you the C is natural and B is flat.

In your example, the flat is to show you the 9th of the chord is flat even thought it is in the key signature. Also, the chord is wrong since a D(b9) has an F♯ in it instead of an F, so the chord is actually a Dm(b9).

  • 1
    I would say it could an altered D7 chord (with a sharp 9 and a flat 9), you don't necessarily need the F# in the melody. If you were to play this melody over the two chords (D7, Dm(7)) you would probably hear that the D7 sounds more familiar (in a jazz idiom). But of course that's subjective.
    – Matt L.
    Commented Oct 16, 2014 at 17:36
  • @MattL. It uses F in the melody in this example. That would clash with a D7.
    – Dom
    Commented Oct 16, 2014 at 17:42
  • 2
    I know that you think so, but that's what my previous comment was about: the F is the #9 of D7, so it is (or could be) an altered sound. And lines similar to this one (F->Eb->D ...) are used all the time over a D7 chord if an altered sound is desired.
    – Matt L.
    Commented Oct 16, 2014 at 17:45
  • @Dom In the spirit of your answer, would you also say that the natural symbol (♮) is kind of an "courtesy accidential", because there is nothing to actually "naturalise" in this case?
    – Marcel
    Commented May 29, 2023 at 19:48

The accidental ♭ does not combine with the ♭ in the key signature to produce a double-flat. Rather, the accidental is redundant. The easiest interpretation rule is that any accidental overrides whatever is in the key signature.

The term for such usage is courtesy accidental:

Although a barline is nowadays understood to cancel the effect of an accidental (except for a tied note), often publishers will use a courtesy accidental (also referred to as a cautionary accidental or a reminder accidental) as a reminder of the correct pitch if the same note occurs in the following measure. This usage varies, although a few situations are construed to require a courtesy accidental, such as

  • when the first note of a measure had an accidental applied to it in the previous measure
  • after a tie carries an accidental across a barline, when the same note appears again in the subsequent measure.

No it indicates B flat. Usually the flat is cancelling a natural (or sharp) earlier in the measure. Even if it's not cancelling, it has only been included by the editor to improve the readability of the passage.

  • In my leadsheet i have some flats in closures while others not. What does this mean?
    – Luke
    Commented Oct 16, 2014 at 16:10
  • 1
    In parentheses? again that is a case where the editor though that that was the clearest way to indicate that that note should be B-flat.
    – Dave
    Commented Oct 16, 2014 at 16:12
  • 1
    @Dave - I find it annoying, as the bar line automatically cancels any earlier alterations, and it clogs up the bar with unnecessary stuff.Helpful ? No !
    – Tim
    Commented Oct 16, 2014 at 16:51
  • @Tim: There are some contexts where it is useful, and others where it is less so. For example, in a key signature with a Bb, if a B natural (marked with a "natural" sign) is tied from one measure to the next, and the next note in that measure is supposed to be a Bb, someone reading the music in the absence of a marking might expect that a "B" without a marking would be at the same pitch as the previous "B" in that measure (i.e. the last portion of the tied note). It isn't "technically" necessary to mark the "Bb", but it's helpful. Similarly, if a B natural in one octave is directly followed...
    – supercat
    Commented Oct 16, 2014 at 18:00
  • ...by a B flat in another octave, there isn't any technical reason why a flat should be necessary, but in the absence of such a symbol a singer might recognize the interval as an octave and (incorrectly) sing it as a perfect octave rather than an augmented or diminished one.
    – supercat
    Commented Oct 16, 2014 at 18:02

No, a B marked with a single flat will only ever be a B-flat.

Occasionally in written music you will see "courtesy accidentals", redundant accidentals meant to clarify or remind the player. These are are often used when a note was altered in a previous bar.


No, a Bb is a Bb, no matter how many times you say so!

One would be required if there had previously been a B natural, in the same octave, in the same bar. If it had been in a different octave, one (maybe in brackets) would seem sensible. In a preceding bar - use your common sense.


Your accidentals (flats or sharps) will add to whatever the key signature specifies. But they generally only affect the musical bar they are appear in, not the entire piece, unless they are then indicated again in many subsequent bars. But why write this complex way? You probably should be writing it in a different key, to get rid of so many accidentals that get indicated, then cancelled next bar, then reintroduced in future bars, making it a nightmare to try and play the piece.

  • Why on earth would you think the asker is composing this? People don't usually write notes they don't know how to read in their works. Or have any say about what key a composer should write their piece in when the composer is someone whom they probably don't know in person and who might even be long dead.
    – Divizna
    Commented Jul 5, 2023 at 1:22

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