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I was wondering if all three of these terms: chromatic, non-diatonic, accidental, all mean the same thing?

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    "Chromatic scale" is a legitimate term. "Accidental scale" isn't. – Dekkadeci Feb 4 at 6:37
  • And there can be "chromatic music" and "non-diatonic music," but we don't have "accidental music" unless we're talking about wind chimes or dogs howling in the neighborhood because an ambulance goes by. – Ben Crowell Feb 4 at 22:48
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The three terms may refer to the same note in a piece but they do not really mean the same thing.

Chromatic refers to out-of-scale half-step movement. For example F to F# in the key of C or to notes that are not within that scale. Chromatic may refer to several notes in a row, C-C#-D-D#-E for example.

Non-diatonic generally refers to notes not in a given major key. The term isn't quite as useful in a minor key piece as the 6th and 7th scale steps are mutable and both versions are often referred to as diatonic (leaving only two notes as non-diatonic in even-temperament).

Accidental refers to the flat or sharp sign attached to a note. A note with such a sign may be called an accidental for short. However, such a note may be diatonic as in the key of D-major, one might have an F-natural followed by an F# (no natural sign on my character set.) Both notes have an accidental applied.

  • I’ve tried to give also an answer. But the question and terms are confusing me more and more: are the signs following the clef accidentals too? Is the sign for the natural note, that resigns an accidental also an accidental? Is a natural g in E a chromatic note or is the g# chromatic? Or both? Or any? What about the blue notes? They are altered down, belong to a definf scale, are they chromatic, or accidentals or non-diatonic? How about enharmonic changes? An f as enharmonic change of e# is it what? So I had to delete my answer not confusing others? Stiil some clearing needed to remove? – Albrecht Hügli Feb 4 at 6:55
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    Chromatic doesn't have to be a half-step movement. An F# in the key of C is chromatic even if the note preceding it is an A and the note following it is a D. Such voice leading is not a chromatic scale, but it is chromatic. – phoog Feb 4 at 19:19
  • a bit confused by the last paragraph. I thought that accidentals were non-diatonic by definition. If I'm in the key of D-major you'd flatten the F# to get to F, but flattening it (ie using an accidental) would now make it non-diatonic. – foreyez Feb 4 at 22:04
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    This seems basically good to me, but in addition to @phoog's quibble, I have another, which is that I believe "diatonic" can be used to refer to a scale built on the diatonic pattern of half- and whole-steps, regardless of whether there is a major key. For example, I think a melody that goes BCDFGEAFEDCABCD is considered diatonic, regardless of whether the tonality is C major, A minor, some church mode, or no key center at all. – Ben Crowell Feb 4 at 22:52
  • @foreyez: I think the last paragraph is right. For example, say you have a piece that starts in G, but later modulates to D The person notating the music can choose whether to notate the later section using accidentals or introduce an explicit change in the key signature. If they notate it using accidentals, then that section is full of C# notes that are accidentals as a matter of notation, but are diatonic in the key of D. – Ben Crowell Feb 4 at 22:55
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Diatonic - belonging to a specific key - as in those notes played in a scale in that key.

Non-diatonic - any other notes which are not diatonic! As in they are not part of the set of notes which constitute a specific key.

Accidental - a sign which changes a note from the original, but retains the same letter name, E.g. B♭ appearing in the key C. It's non-diatonic, so the B gets changed with an accidental into B♭; F ♯ appearing in the key C. It's non-diatonic, so the F gets changed into F♯; Bnat. needs a natural sign in the key F, as diatonically, there's B♭. On certain occasions, ♭♭ and x are used to denote doule flat and double sharp. They also are know as accidentals.

Chromatic - any note which is non-diatonic, and will need an accidental sign to qualify it in a key.

Note (!) the signs at the beginning of a piece which we call the key signature are not accidentals - they're there on purpose! Called - the key signature.

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  • Accidentals are signs as flats (b) and sharps (#) usued for alteration of the tone pitch, also the sign for a natural tone. The altered notes may also be called accidentals.

  • Non-diatonic are the tones that are outside of a given scheme (scale) of whole tone - and half tone steps. Sometimes they can be identified by the accidentals.

  • The chromatic scale consists of 12 half tone steps. Notes that don’t belong to a defined scale are chromatic.

  • Altered tones, notes with accidentals, can be chromatic tones or non-diatonic or both. The term “chromatic” describes the new color given by an alteration.

    The more I know ... the more I know that I know nothing!

  • but the moment I see an accidental, I can assume the resulting pitch is non-diatonic? – foreyez Feb 4 at 22:06

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