8

Key of C Key Signature has no symbol, so say I was notating music in G Major then wanted to change to the Key of C, how would I show this?

9

Removing accidentals in the key signature is done with the natural symbol. Put a natural symbol on the position of each accidental you want to cancel, and reiterate the ones that are left.

enter image description here

In the above:

  • Cmaj cancels all 3 sharps of Amaj.
  • Gmaj cancels 2 sharps of Amaj and reiterates the one left.
  • Fmaj cancels the sharp of Gmaj and notes the new flat.

As Tim notes in his answer,

  1. adding double bar line before the key change is correct notation;
  2. with many accidentals, the change can get pretty long: enter image description here
  • I can't imagine any composer wanting to modulate from seven sharps to seven flats (or vice versa), but my classical favorite Gustav Mahler did 6♯ → 6♭ in his unfinished 10th Symphony. – pr1268 Feb 21 '17 at 10:07
  • @pr1268 7 flats is C♭ major, which is the enharmonic equivalent of B major, which is 5 sharps. So from 7 sharps you can modulate to 5, and then modulate enharmonically. It's not far fetched. Ditto for the opposite direction. – user1803551 Feb 21 '17 at 10:26
8

You create a new signature containing just of one natural sign on the same line, where the sharp was before, so nothing remains in effect.

See als my answer to closely related question for more details.

enter image description here

3

It's normal to cancel the previous key signature, so a natural sign (♮) on the F line(s) will be sufficient.

Going the other way (i.e. from C to G) will require merely a ♯ sign on the 'F' line. With more ♯s or ♭s, the new key signature will have naturals cancelling the previous unwanted ♯ or ♭ — a weird key signature with more info than usual!

I tend to put a double barline (both thin) at that point, as it's often the start of a new part anyway, but also to point out the key change clearly … especially in C to something else, or something else to C. Obviously going from lots of ♯s/♭s to C will show up as lots of naturals, though.

  • Not really "weird" with "more info that usual". Historically, naturals were always written to cancel existing sharps or flats in a new key signature (even when going from say 4 sharps to 2 sharps). However the modern convention is that this is only done when the new signature has no sharps or flats - i.e. C major or A minor. – user19146 Feb 20 '17 at 7:52
  • @alephzero - by weird I meant we're used to seeing only #s or bs in any given key sig. Not a mixture (except for a key change...). – Tim Feb 20 '17 at 8:13
0

Current practice is to insert enough naturals to cancel the previous key signature when moving into the open key. Otherwise just put the new key signature.

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