If I find the key signature contains, let's say, E flat, does that only mean only E's are E flat or every note on the staff of the key signature are flats? I've looked up multiple things but I am not having any success.

3 Answers 3


When at Eb appears in a key signature, it means that every E appearing in that music — no matter which line or space it is written on — will be played as an Eb unless otherwise indicated. The Eb in the key signature does not affect any other note.

In a key signature, each letter-named key (a "pitch class") gets its own sharp or flat.

For example, in the key signature below, every B and E in the piece would be played as Bb and Eb, but all of the other pitch classes (A, C, D, F, G) would be played as usual, without alteration. The flat signs affect, for example, an E written on the bottom line of the staff, or a B written above the staff.

Bb major / G minor key signature

In a piece with the above key signature, if a B or E natural is needed, then a natural sign would be placed before that note at the time the change is required.

  • thanks, I'm still a little confused. you saying that all the notes that appear on the key signature will be played as flat right
    – kian myers
    Mar 9 at 1:19
  • 1
    @kianmyers Yes, that's right.
    – Aaron
    Mar 9 at 1:37

Showing just one flat (on E) in the key signature couldn't possibly indicate all notes are flat. That would be madness, and non-sensical!

Maybe it's the way you've phrased the question.

When the key signature shows just one flat in one place on one staff, it's shorthand for all those notes with that letter name (pitch class) to be affected throughout the piece. In other words, a flat sign on top space, treble clef, means not just those Es, but every E in every octave in that piece must be flattened. If needed, some could be natural, but would have to be signalled as such where they are.

As an aside, where there is an E♭ in the key signature, there's sure as heck going to also be a B♭ - having both signifying keys B♭ major or G minor.

  • In proper "formal" music notation, the key signature will appear at the start of each line for which it is applicable, but to expedite transcription of parts which would probably be sight-read once from start to finish and never used again (e.g. parts for simple advertising jingles) it is acceptable to include the key signature on only the first line where it is used. Having key signatures at the start of every line can be very useful if someone may need to start reading a piece of music in the middle, but if one is writing out ten parts with eight staves each...
    – supercat
    Mar 9 at 16:31
  • ...of a piece in Eb major (three flats), and it takes 1.5 seconds to draw each flat sign, writing out all the extra key signatures would require an extra five minutes of work. This convention has been extended to some printed music which is supposed to appear informal, such as the Real Book.
    – supercat
    Mar 9 at 16:34
  • @supercat - I used to work with a band which used numbers with key sigs, only on the first line - and the #/b were usually in the wrong places! It didn't really matter, as we all knew 3# = A, etc. But I often question why the key sig. needs to be stated on each line. Time sig. isn't! Obviously if there's modulation/key change, it needs showing, but...
    – Tim
    Mar 9 at 17:13
  • If musicians will often start playing in the middle of a piece (e.g. during practice or rehearsals), that will be greatly facilitated if the marks are printed at the start of each line.
    – supercat
    Mar 9 at 17:23
  • @supercat - I'm doing that all the time. If I'm not aware of that detail, really, I shouldn't be there.
    – Tim
    Mar 9 at 18:01

My music theory is not super strong, but I'm going to put this out there as a baseline answer to be improved by the community...

For the sake of argument (and to make intervals more visual), I'm going to use a piano keyboard for explanation.

enter image description here

If you are playing in the key of C Major, there are no sharps or flats. So first you play the C on the far left, then the D, then E, and so on, pressing all the white keys.

In case you don't play piano, I will point out that the musical distance between each adjacent key (black or white) is a half step. So if you count out the distance between the keys you play in the key of C on a piano, you get a whole step from C to D (C, C#, D), then another whole step (D, D#, E), then a half step, etc. So all together you get whole-whole-half-whole-whole-whole-half to make up the entire C Major scale.

Anytime you want that "major" sound, you can construct a major scale from whatever starting note you want, you just have to follow those same relative gaps between notes. So if I wanted to start with B♭ and make a major scale, I would do the same pattern whole-whole-half-whole-whole-whole-half: B♭ is the first note, and then going up a whole step we get C (B♭, B, C). After following the whole pattern you should get B♭, C, D, E♭, F, G, A, B♭, arriving back at the root note of the scale.

You'll notice that in the B♭ Major scale we've constructed, there are two flat notes: B♭ and E♭. If you want someone to play a piece of music in this key, you would mark those two flats on the sheet music, just the way Aaron describes. The person playing the sheet music would understand that they are playing in B♭ Major, and they will know that no matter what octave they are playing in, they must make sure they play B's and E's flat.

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