Just wondering if accidentals in music can be seen as a temporary change in scale. There's a lot of scales that have just one note difference, so they sound good when they're interchanged temporarily. For example, Phrygian to natural minor is just a one note difference, Dorian to natural minor is also just a one note difference, and so on.

For instance, in Chopin's Nocturne Op 9 No 1 in B♭ minor in the first measure there's an accidental on the fourth note. But it's really just a change from B-flat natural minor to B-flat harmonic minor, which has the A note, which isn't in the natural minor.

The opening two measures of Chopin's Nocturne Op 9 No 1 in B-flat minor. In the first measure the right hand plays the notes B-flat, C, D-flat, A-natural, B-flat, G-flat

So when there's an accidental in music does it usually indicate that there was a temporary change in scale?

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For instance, in Chopin's Nocturne in B-flat minor in the first measure there's an accidental on the fourth note. But it's really just a change from B-flat natural minor to B-flat harmonic minor, which has the A note, which isn't in the natural minor.

This idea makes the assumption that Chopin intended to compose music in something called the "B-flat natural minor scale." I would instead make a different assumption based on actual historical practice of composers like Chopin: pieces written in minor keys typically contained many chromatic notes (particularly variants of the 6th and 7th scale degrees) as their standard "scale" (to the extent that they had one). Until the mid-19th century (and the introduction of a new kind of "modal" music), they almost never composed in the "natural minor scale." Nor did they compose in the "harmonic minor scale," though perhaps they came closest often to composing in the "melodic minor scale," but even that's an abstraction.

The scales learned by beginning musicians are diatonic approximations to the most common notes used in musical practice within a given key. That doesn't mean that other notes can't appear within that key.

And it's pretty typical for historical classical pieces from the 18th century through today to contain all twelve chromatic notes as part of their "scale," just serving particular functions. (That is: minor keys in classical style inevitably make use of both raised and lowered forms of scale degrees 6 and 7. The raised 3rd and 4th scale degrees are frequently employed as V/IV and V/V, even without a change in key, but just as chromatic variants. And the lowered 2nd scale degree is frequently part of Neapolitan chords.)

Chopin could easily use all twelves notes of the chromatic scale without leaving the central key of tonic.

Normally, when music theory discusses a "change of scale," it implies something more than a single chromatic pitch (or even a lot of them). A "change in scale" means that one or more foundational pitches in the current key has undergone a transformation to something else. For example, a piece that modulates from B-flat minor to F minor will see alterations from G-flat to G-natural as central notes, as well as the addition of E-natural as a common leading tone (while A-natural will be used less frequently).

Or, more rarely, perhaps a foundational pitch has been completely omitted or another has been added. In that case, sometimes no accidentals are necessary to observe some sort of change in scale.

On occasion, even a single accidental can sometimes be seen as a temporary change in scale, particularly if it seems to effect a temporary tonicization that reaches out of the current key.

But the A-natural in the question isn't reaching outside the key. In fact, it's providing the most common and necessary form of the note A that defines the key of B-flat minor, i.e., the leading tone. Without that accidental occurring in the appropriate locations, a classical piece would generally not even be considered to be in "B-flat minor" of any normal sort.


Sometimes it does, sometimes it doesn't. Sometimes an accidental is just a change in pitch. For example, it doesn't make a lot of sense to see a chromatic run as a sequence of jumps around the circle of fifths (listen to the famous "Entry of the gladiators" by Fučik which uses lots of chromatic sequences over a quite simple harmonic framework).

Sometimes there is ambiguity between note changes and scale changes: that kind of ambiguity is actually a lot of what music is about. And sometimes the scale can change without even employing a single accidental (namely when the tonal focus changes but the note which would have to get an accidental is not being sounded).


An accidental means either a temporary scale change, or an out-of-scale passing note. But accidentals are only written for explicitly written notes. The lack of an accidental does not mean that there couldn't be an implied temporary scale change. For example if in a song that's in C major, there's a D7 chord (which has an F# note) in the harmony, but the melody does not happen to have an F# during that chord, then there is no accidental to be seen.


No, not normally. There are, in 12tet, 12 notes available to make tunes out of. Basically, 7 of those are used - the diatonic notes. But if a composer decides that one of the other 5 need to be played, he'll use it. But to do so, it needs writing as an accidental, as it's not in the set of diatonic notes for that key. It certainly doesn't mean suddenly there's a change of key - merely a change of note!

There are times, though, when a piece does modulate, or does change key. It may be more convenient for the writer to keep putting in accidentals for one or two notes that have 'become diatonic' in the 'new key'. So if one sees that happening, then yes, one could guess it's due to a key change. If it's for a long time, it makes more sense to change the key sig., but for a few bars, it's just not worth it. Accidentals come to the rescue.

And yes they're always going to be a temporary change of scale - perhaps a better term might be key?

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