Is there a term for the group of non-natural notes, i.e. notes altered with sharps or flats?
1@LeeKowalkowski Not if they are in the signature.– ÉdouardMay 14, 2014 at 11:02
1As in, notes outside of the key, or literally, a collective noun for the notes represented by the black keys on a piano?– Lee KowalkowskiMay 14, 2014 at 11:07
1@LeeKowalkowski: That is the question... It is easy to implicitly reason in the key of C, but if such a term exists, I think it will be generalized to other keys. I asked the question since I wanted to name this group something other than non-naturals in a program, so that would imply the black key interpretation.– Meaningful UsernameMay 14, 2014 at 11:11
2@LeeKowalkowski You don’t put notes in the signature, but if there is a C♯ in the signature, then a C♯ in the piece is not an accidental. A C♮ is.– ÉdouardMay 14, 2014 at 11:12
1@MeaningfulUsername Oh, so you are talking about notes outside the key?– ÉdouardMay 14, 2014 at 11:13
I’m a french speaker, as such I usually call (double) sharps/flats “alterations” — which I’ve found in the Lilypond glossary, but seldom anywhere else. “Altered notes” thus seems perfectly reasonable to me.
1) On the one hand, you can denote which tones should be flattened or sharpened by default. This is typically done by writing those sharps and flats at the beginning of the staff, after the cleff, but before the time signature.
This is commonly referred to as "key signature". This is a bit of a misnomer since the key signature alone is typically not enough to deduce the key. Key signatures can appear halfway a staff too, but the principle is the same.
In relation to your question, the purpose of the key signature is to define which tones are "natural" to use your term; that is, it sets a standard for which sharps and flats are implied for the section to which the key signature applies, and it results in a more clear notation since those flats and sharps then don't need to be explicitly denoted.
2) Then there are accidentals. Accidentals are notes that are raised or lowered temporarily, deviating from that what is implied by the key signature. Note that this may be done either by sharpening or flattening a note, but it may also involve adding an explicit natural sign in case that tone was raised or sharpened by default, as implied by the key signature.
Accidentals might indicate tones that are outside of the current scale (or key, or both). However, that need not be the case. In the melodic minor key comes in two flavors: the ascending flavor has a major sixth and major seventh, whereas the descending one has a minor sixth and seventh.
Typically the major sixth and seventh need to be denoted by accidentals in order to raise them with respect to what is implied by the key signature.
For example, a key signature with one sharp may indicate E minor. The one "default" sharp in this case is f#. In such a piece you will often find accidental c# and d# (which are the major sixth and seventh of e respectively). And if the key signature would have, say, 3 flats to denote C minor (b flat, e flat and a flat), then you might find a natural a and b, which restore the all notes on a and b lines from their former "flattened" state (as indicated by the key signature) back to their natural sound.
3) Sometimes, accidentals are applied to indicate sounds that are outside the current scale. An example is chromaticism, which "fills" the gaps between diatonic scale degrees with semi-tones that are themselves not in the scale. The notes themselves are, to the best of my knowledge, still called "accidentals". But when you talk about the harmony that is implied by the cords that have these out-of-scale notes, I think then the term is to talk about "alterations"
For example, esp. in the minor mode you might encounter a so-called Neapolitan sixth chord. This is the first inversion major triad on the minor 2nd degree. Let's say you're in A minor (key signature with no flats, no sharps), then a first inversion major Bb chord is the Neapolitan sixth. The root of this chord is Bb, and this is referred to as an "alteration". The in-scale chord on the 2nd degree would be the diminished triad b-d-f, and by alteration, which diminishes the major 2nd to a minor 2nd, and the chord becomes a major triad bflat-d-f.
So as a chord note, the b flat is called an alteration, but the denotion of the b-flat is simply an accidental.
The term "chromatic" is probably better than "altered", or at least more specific to the idea of being outside the key. May 15, 2014 at 14:46
@PatMuchmore I was thinking a bit more about it, and was wondering what to do with modal sections. Say, a piece that is fairly straight in C major, but which has lydian and/or mixolydian sections. I hesistate to call the accidentals to achieve those modes chromatic. But by definition, they are out of scale. May 15, 2014 at 15:12
No, if you're in C Lydian, then F# is diatonic and F-natural is chromatic. In C Mixolydian, Bb is diatonic. Diatonic refers to whether the notes belong to the key, whether that key is in a major, minor, lydian or locrian mode. I take your point though, often the difference between a modal shift and a brief chromatic coloration is anything but clear. The concepts are quite black and white, but the actual contexts are often highly ambiguous, and one could make strong arguments either way. May 15, 2014 at 17:11
@PatMuchmore Thanks! I see - it seems I need to adjust my understanding of the term "diatonic" - I thought that simply meant "major" or (melodic) "minor", as a contrast to "modal". But it seems it applies to any scale built out of both major and minor seconds. May 15, 2014 at 22:42
when the context is the major key, a note that is not part of the key is called a non-diatonic note.
+1 for the term non-diatonic. However I thought it simply applies to all tones that are "out of scale", also in minor mode. (That would exclude raised or natural 6th and 7th, since they are simply part of the scale) May 15, 2014 at 5:43
See @Matthew Walton's answer. "Non-diatonic" is fine, but the word "chromatic" already exists for this meaning. Notes that belong to a key are diatonic and notes that don't belong are chromatic. Roland Bouman, as Matthew notes in his answer, the raised sixth and seventh scale degrees in minor are considered to be diatonic because—although they're outside the key *signature*—they aren't outside the key itself. May 15, 2014 at 14:45
In my experience (playing mostly early music in the UK) they're called 'chromatic' notes. This is from the term 'chromaticism', and the idea that throwing in the occasional extra sharpened or flattened note adds 'colour' to the music. The chromatic scale, of course, contains all these possible notes.
Note that this not the same as a piece in a minor key which notates the necessary sharpened or flattened sixths and sevenths as accidentals (because they're part of the minor scale and so aren't chromatics), or a piece which changes key without changing the key signature in the notation.