We are aware that an accidental is a sign which changes the pitch of a note usually stated in the key signature, like a natural sign before a C in key D makes that into C♮, etc. Sometimes even the key signature is said to contain accidentals (I'm sceptical).

The first two notes that needed them were B and F, and the Germans cunningly got round the B by introducing another letter. F didn't fare so well, and F♯ was born, followed by other re-incarnations.

However - it's the etymology that's in dispute for this question. Whenever accidentals are used, they're never used accidentally! It's always on purpose! So the word itself is a misnomer, and would be confusing if we didn't know any better. It probably confounds beginners, too. So, where and why, and by whom was it coined. And is there a more concise word instead?

I've come across inflection in the Oxford Companion to Music, which seema to cover all the 'accidentals'.

  • More concise, eh? Sharp, flat, chromatic, borrowed... As for accidental, it's likely the fact that it doesn't occur in the diatonic scale — intentional of course, but one can always hear the surprise in it. One certainly expects that this "rule-breaking" was originally discovered accidentally. :p And I agree about key signatures— they're a misnomer there. Commented Apr 11, 2021 at 12:58
  • 3
    As for etymology, Etymonline explains it via the older sense of "accident": something non-essential, happenstance. Today we might say "incidental" instead for that meaning. The editor reasons that the accidental is incidental to the music — does not affect the key it's in. Commented Apr 11, 2021 at 13:03
  • My piano teacher used to call them "accidentally on purposes"
    – Tetsujin
    Commented Apr 11, 2021 at 13:12
  • "the Germans cunningly got round the B by introducing another letter": originally the B flat was denoted with a rounded letter B and the B natural with an angular or "square" letter B. (The round one was considered "soft" and the square one "hard," which would also have later significance.) The Germans reinterpreted the two forms of the letter B as distinct letters, calling the square one H. I don't know whether this happened before or after the development of the flat and sharp signs.
    – phoog
    Commented Apr 11, 2021 at 14:33

4 Answers 4


The term "accidental" comes from the (probably Medieval) Latin "accidentem" meaning "outside the usual state of affairs" or "by chance" and appeared in music in the 1400s.

  • from "Online Etymological Dictionary"

The term "accidental" often indicates that a property is not essential to the discussion. The music meaning is the same, the note names and intervals are not changed by accidentals. The note F# is still "some type of F" (as is Fb). The interval D-F is a third as is D-F#. One is minor, the other major but they are still thirds. Similarly, D-F## (double sharp) is an augmented third and harmonically different from D-F or D-F#. (The notes F## and G are only identical in equal or some other temperaments.

  • I chose this as an accepted answer, but it's bereft of a reason why the key sig. 'has sharps or flats'.
    – Tim
    Commented Jul 6, 2023 at 10:21

The sub-topic, which addresses terminology of "signs" in key signature was already discussed quite extensively in this question. English is somewhat handicapped here by not providing a separate word for the sharps or flats of the key signature, which other languages do.

The remaining issue seems mostly to be a mental interference of two unrelated meanings of accident[al], see e. g. Collins, where the meaning related to music lacks any mentioning of word like random, by chance.

So what is left open seems to be, why such a strange term was considered as appropriate centuries ago and why it never got replaced, but this seems more a question of linguistic than music.


I think we need to focus on more meanings of 'accidental'. As well as 'by chance' it can mean 'incidental' or 'subsidiary'. These fit the musical definition rather better.

So 'accidental' is an apposite name for those incidental sharps, flats and naturals. But @Tim also asks for a more concise one. 'Acc' could be mistaken for 'acciaccatura'. 'Ac' could be 'accent'. Perhaps start from the other end and call it a 'dental'?

  • I tried the dinosaur book (Roget's Thesaurus) offline and found nothing better. It's similar to the problem with secondary dominants (dominants made "secondary" chords); earlier used of applied dominant or attendant dominant were used in the 1800s. (I like "applied" but I don't usually suggest changing what works.)
    – ttw
    Commented Apr 11, 2021 at 15:21
  • Nothing like drilling down and extracting a good alternative... Actually, 'incidental' seems more apposite. Thanks.
    – Tim
    Commented Apr 11, 2021 at 15:49
  • Only if you have tunnel-vision about the meaning of 'accidental'
    – Laurence
    Commented Apr 11, 2021 at 16:55
  • +1 "Incidental" is the perfect word to describe what is meant by musical "accidentals". The modification of the note occurs for a specific incident, then reverts back to normal in the next measure.
    – WillRoss1
    Commented Apr 20, 2021 at 16:39

Sharps and flats are used as key signs and as accidentals.

The accidentals came up in medieval music when melodies were tending to need a leading tone. This could happen as a change note within a tetrachord or at the end of a song to confirm the finalis (clausulae).

We can assume that they were primarily played and sung by the performers or the organist shown by hand signs. They were optional notated and in later notations by other music researchers marked in parenthesis (+) to indicate an optional augmentation e.g. the seventh degree in hypomixolydian. The b flat (b-rotundum) was alternately to (h=b-quadratum=B-natural e.g. the fourth degree in lydian. In German the B natural is H.

They could have played accidentally because they were optional and not expected.

Since the well-tempered keys came up, sharps and flats aren‘t optional anymore and can‘t be played just accidentally, because it will be a fault if the aren‘t respected or overlooked.

So I agree that the term accidental is misleading and confusing, while sharp and flat means the effect of the changing interval or tune.

In German we say Vorzeichen for the key signs and Versetzungszeichen for accidentals, which implies alteration up or down. Sharps and flats are labeled by their shape: Kreuz (cross) and B (b).

I don‘t want to extend this answer to the naming of the chromatic altered key names. This might become even more confusing than the problem of the alteration signs that you call accidentals. :)

  • 1
    Tetrachords are not particularly relevant to the early use of these signs, nor to the concept of b quadratum and b rotundum; the applicable theory is that of the hexachord. And the signs that came to be known as accidentals do not "change the note within the [hexachord]"; rather, they change the identity of the hexachord to which the note belongs. (Any altered note other than B flat will have to come from a hexachordum fictum, however.)
    – phoog
    Commented Apr 11, 2021 at 21:31
  • 1
    I agree: hexachords. Commented Apr 12, 2021 at 8:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.