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Could it happen, that there would be C# in the key signature but no F# ? (or in general any higher # without lower one.)

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  • G# major/F minor is one example. Has c# but not f#. For me being a guitarist, visualizing fretboard allows me to easily solve this. Feb 5 at 13:02
  • It seems G# major/F minor are the only keys which have c# but not f#. Feb 5 at 13:15
  • 3
    @marshalcraft - Technically true, although it does have an Fx, but G# major is not a standard key (it is conceptualized instead as Ab major). f minor does not have a C#, it has a Db (same tone, different notation). en.wikipedia.org/wiki/G-sharp_major Feb 5 at 14:05
  • 1
    Okay thank you I learned something. Us guitar players walk while piano players ride a horse. Feb 5 at 17:29
  • @marshalcraft Although F minor does not, but E# minor does (relative key to G# major, so the same key signature). It sounds exactly the same as F minor (enharmonically equivalent).
    – trolley813
    Feb 6 at 9:15
24

It's possible, but extremely unusual. Béla Bartók was one composer who sometimes wrote things like this. For example the study no.99 in volume IV of his collection of piano studies "Mikrokosmos" he writes a key signature of just an E-flat in the right hand and a key signature of F-sharp and G-sharp in the left hand.

17

You can do this, but imagine yourself in the performer's seat. If you hand out sheet music whose key signature is unfamiliar it will immediately raise questions:

  • Is this a misprint?
  • What key am I actually in?
  • Why's it been written like this?

And the answer might be "Weird! I don't trust this sheet music".

Whilst it's always been possible to read the accidentals from a regular key signature, mostly we don't; instead we see there are three sharps or whatever and know what notes to modify as we read the stave. Non-standard key signatures aren't as comfortable to work with.

You'd achieve the same sound by using a standard (non-depleted!) key signature and placing naturals in front of some of the notes.

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  • 3
    If I recall correctly, the pieces in Mikrokosmos that have unusual key signatures have explicit notes on them saying "yes, this key signature is printed correctly". Feb 4 at 21:04
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    @MichaelLugo it might depend on the edition, but in the Boosey & Hawkes edition there is no explanation.
    – PiedPiper
    Feb 4 at 22:11
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    (The parenthesis is emphasized, but perhaps also ambiguous.) Does "depleted key signature" refer to C major / A minor irrespective of the tonality (i.e., laziness to identify a reasonably matching standard signature), or does it simply mean "non-standard", or is that a term that means something specific? Feb 5 at 12:11
  • I hope I can clear up any ambiguity. By "depleted" I meant a key signature that is non-standard because sharps/flats that you might have expected to see aren't actually there. For instance, if I see a key signature containing just a G# I'd consider it depleted because at the very least I'd have expected to see F# and C# there too. Feb 5 at 12:41
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    An alternative to a non-depleted! key signature with naturals used as needed is the key signature without the extra sharp (a key-signature of nothing, in the OP's case) with sharps added as needed.
    – Rosie F
    Feb 6 at 8:09
7

I've seen this.

In my case, the context was playing folk music from Eastern Europe and the Middle East. Here, scales other than WWHWWWH are common, as are "interesting" compound time signatures, like 11/8 etc...

An example I remember was a piece in D minor using the harmonic scale, so the key signature had Bb and C#. It saves on accidentals, and once you become used to it is perfectly acceptable to work with.

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    A important point here is “once you become used to it”. For genres/traditions/subcultures where most performers are used to it, it’s fine. In other traditions (including the mainstream classical, pop, and jazz traditions) most performers are not familiar with it, and will be unhappy with it, as described in other answers. So it’s a very context-dependent point.
    – PLL
    Feb 5 at 11:57
4

Not if you are following standard notation for the conventional, European-based major, minor or modal key signatures. In all such scales, the sharps follow a set progression. This ensures that any note that can be notated without accidentals can be played in a scale whose notes are in the same relationship to each other as the white keys on a standard piano. In other words, the standard key signatures all define scales with the familiar whole step, whole step, half step, whole step, whole step, whole step, half step progression (although they may start at different places in that progression). There is no way to map that to a key signature with a C# and an F natural (there's too long a run of whole steps). There are some keys with a C# and an Fx (double sharp), but those are considered non-standard, and are usually mapped to equivalent scales that use flats instead. (As noted by @supercat in the comments, there is a different pattern of steps that would give you an F natural and a C# in the d harmonic or melodic minor scales, but that would not be reflected in the standard notation for the key signature, but instead, would be covered by accidentals as needed.)

If you are departing from the above assumptions, you can have any key signature you want. There are other cultures that do use different scales in "nonstandard" keys, as well as some adventurous composers who have invented their own.

It's worth noting here that the way pianos are tuned represents an almost wholly artificial ("tempered") scale designed around the (dubious) goal of making sure that every standard key signature sounds exactly the same (relatively) as every other. With "natural" tuning, this wouldn't be the case. (In natural tuning, it's also not true that B# is the same note as C or that Fx is the same note as G.)

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    Note that the D harmonic minor scale would contain a C# but no F#, but the normal way of notating music in D harmonic minor would be to use a key signature with one flat (D natural minor), and then use accidentals for every C#.
    – supercat
    Feb 5 at 20:35
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    “Not if you are in a standard, European-based major, minor or modal key” is a pretty good extension of what I’d have answered: Not in MuseScore, but if you’re leaving our usual system of notation, all kinds of things are possible. (I count G♯ major as having an F♯ which is just later overlaid by the 𝄪 sharpening it again.)
    – mirabilos
    Feb 5 at 21:53
  • Just to show how weird it can get: "Key signatures of up to one triple-flat + six double-flats = 15 normal flats appear in pp. 141-170 of T. Dumitrescu's 'Constructing a Canonic Pitch Spiral: The Case of Salve Radix.' In Canons and Canonic Techniques, 14th-16th Centuries, ed. Schiltz & Blackburn." Feb 7 at 2:10

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