In the image below, the key is initially G, then changes to E (right?) for the rest of the song. However, that entire bar uses sharps from E, and the key never changes back. Why wouldn't the key change happen before that bar? Previous bars do indeed play notes from G, so it makes sense for it not to happen even sooner.

The source is "Jane's Song", by Christopher Norton.

enter image description here

  • I'd guess these two bars are the transition from the part in G major to the part in E major. Does the musical theme change with the key? Maybe the bars in question did better fit to the previous theme?
    – Arsak
    May 21, 2019 at 10:58
  • That makes sense. The song has a strong ABA structure, and the last bar is part of the B for sure May 21, 2019 at 11:13

2 Answers 2


It happens there because the previous bar isn't in E. The remaining part is, but that bar itself is the V of E, thus B major, leading into the new key. It could have been written as in the new key of E, but as the final part of the last section, it stays in G, complete with necessary accidentals.

  • Far too soon to accept the answer! Hang fire!
    – Tim
    May 21, 2019 at 12:34
  • Why should we hang fire? Your answer is correct and useful. May 21, 2019 at 16:19

Tradition. Time was when composers wouldn't always change key signature even when there was a clear change of key. For example, it's usual in Classical sonata-form movements for the second subject to appear first in a different key from the first subject, but the key signature to stay the same even if a change would mean easier notation. A striking example here is Beethoven's piano sonata 21 in C ("Waldstein"), where the second subject's first appearance is in E major, entailing about a hundred accidentals. In that era, composers seem to have regarded key-signature changes as suitable only at points that are important in the movement's structure. And what would indicate the close of one section and the start of another? A cadence that indicates a change of key -- as Tim suggests in his answer.

Here are two examples from the first movement of Beethoven's piano sonata 8 in c minor ("Pathétique"), where the music leading up to the key-changing cadence entails several accidentals but the key-signature doesn't change until the cadence itself.

At the start of the development, where the key is already g minor, and modulates to e minor:

Beethoven PS 8 c m1 start of the development

In the transition from the development (which modulates through various keys) to the recapitulation (in c minor):

Beethoven PS 8 c m1 end of the development

Composers would later get less reluctant to change key-signature (including Beethoven himself) but the legacy of this old tradition remains to some extent.

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