Why is it deemed necessary to put the key signature at the beginning of each line? And in the same vein, why do we need a time signature at all, when it's fairly apparent what it will be in the first bar or two? Or, a slightly different slant, as common time is so common, use that as default, and only write in other time signatures.

  • 2
    I don't know about your first question, but for the second, I can imagine circumstances where it is not immediately obvious what the time signature would be
    – Doktor Mayhem
    Jul 16, 2016 at 17:33
  • I'm assuming a 'standard' piece where the timing is static.
    – Tim
    Jul 16, 2016 at 17:38
  • Whether it's "fairly apparent" depends on the style of music you are playing. If you are in an orchestra pit looking at a part that starts with 32 bars rest and then has a succession of one dotted half note per bar (and nothing at all in your part that resembles "a tune"), how would you know whether to count the rests as 3/4 or 6/8?
    – user19146
    Jul 16, 2016 at 17:56
  • @alephzero - I'd hope the player might have spent those 32 bars listening! If by then, they hadn't got the feel, what were they doing there anyway?
    – Tim
    Jul 16, 2016 at 18:07
  • Would you apply the same logic to the clef, which is also repeated at the start of each line?
    – JimM
    Jul 16, 2016 at 20:47

3 Answers 3


The time signature cannot be figured out from the content since both 2/2 and 4/4 have a whole note all-in-all but have different accents and drive. It's even worse with 6/8 and 3/4.

The repetition of the key signature is just a visual reminder since the key signature pervades a piece. If you start the piece from the second page, it would be really awkward to have to leaf backwards in order to figure out what notes to play. Having each line "grounded" in its key signature makes it easier to be sure about what one is playing.

Arguably that would also hold with the meter. Convention still has converged to not repeating it, just like one does not repeat a tempo mark like "Allegro".

  • Why would youy start from the second page? O.k. put the key sig. on each page. But then why not put the time sig. on each page, too? Each line doesn't display the time sig. anyway. Other points only back up the question.
    – Tim
    Jul 16, 2016 at 18:11
  • Correction Allegro is a character mark not a tempo mark.
    – Neil Meyer
    Jul 16, 2016 at 18:34
  • @NeilMeyer - that doesn't alter the point one jot. On my metronome it's marked as a vague tempo.
    – Tim
    Jul 16, 2016 at 19:53
  • 6/8 and 3/4 are usually written out in different groupings. 6/8 will have 2 groups of 3 quavers, and 3/4 will have 3 groups of 2 quavers. So it's not difficult to recognise each.
    – Tim
    Jul 17, 2016 at 5:14

Sure, you can generally discover the time after a few bars. But why not know it BEFORE the first note? It will make more sense of the conductor's upbeat when sight-playing, if nothing else.

There's a "fake book" style where after the first line not only time signature but also key signature and clef are omitted. It's not helpful, particularly in e.g. a Broadway pit orchestra part where both key changes and cuts are common, so you can find yourself cutting into a different - unstated - key! Some old-timers find the style "professional", though I think the only professional aspect was corner-cutting by paid-per-bar Union copyists.

  • If there's a change in signature, it's paramount that it's stated. Without it, the piece is unplayable! I've played hundreds like this, and feel that one only needs a statement at the beginning of the piece or when a change occurs.
    – Tim
    Jul 16, 2016 at 18:05
  • Yes, as I said, fake book style has its supporters. Another argument against is that Sibelius doesn't do it easily. And surely no-one MINDS seeing a key signature on each line. Another feature of fake-book style is a fixed 4 bars-per-line. So it can't even be argued that omitting clef and key signature get more music on the page. There's also the 4 bars-per-line proportionally-spaced thing for jazz lead sheets, which sacrifices some readability of the notes in order to achieve metrical spacing of the chord symbols. Useful when you're "playing the changes".
    – Laurence
    Jul 16, 2016 at 18:15
  • I've written music out for too many years with 4 bars per line - a bit like (real) poetry. Very easy, generally, to read. Part of my point is that if there needs to be a key sig. on each line, then why not a time sig.? If there's no change, why tell everyone? It's clutter, rather like putting a # back after a natural, when the barline does it anyway.
    – Tim
    Jul 16, 2016 at 18:26
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    I suppose the clinching argument is that a key signature on each line is standard notation, except in one genre of American commercial music. No-one will play a wrong note because the key signature's there. Some might if it isn't.
    – Laurence
    Jul 16, 2016 at 19:22
  • If one is in the middle of playing a piece, one should be thinking in that key, surely. Should one need reminding of that any more than 'by the way, we're in 6/8'.
    – Tim
    Jul 16, 2016 at 19:51

Even in cases where you can figure out the time signature (there are cases where you can't), the part is not supposed to be a puzzle. It's supposed to make things as clear as possible to the player.

Key signatures can often change so it's good to be reminded at every line what the current key signature is. Sometimes, on lead sheets of simple tunes that have no key signature changes, it's only written on the first line.

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