Related
Metre covered the principle; this entry covers notational practice.
Where it goes
The order at the head of a score is fixed:
clef → key signature → time signature → first bar
| Order | Why |
|---|---|
| 1. clef | first fix which line is which note (see [[concept:clef |
| 2. key signature | then fix which notes are altered by default (see [[concept:key-signature |
| 3. time signature | finally fix how beats are counted |
The order is not arbitrary: from pitch positions, to defaults, to the organisation of time — each step builds on the one before.
The two letter signs
Sometimes a letter appears instead of numerals:
| Sign | Equals | Note |
|---|---|---|
| C | 4/4 | commonly read as common time, but it is in fact a remnant of medieval notation (the sign for "imperfect time"); the pun with "common" is a later rationalisation |
| ¢ (C with a stroke) | 2/2 | called alla breve: read with the half note as the beat, hence two beats per bar |
The second row deserves a second look: ¢ and C differ in both numerator and denominator (2/2 against 4/4), so they are not the same metre: ¢ has a larger beat unit and sounds more flowing, faster.
On the origin of C, be precise: it descends from the medieval system of mensural signs (denoting imperfect duration), later used interchangeably with 4/4. "Common time" is a later folk explanation, not its etymology. (These gaps between a term and its origin are common in music — see the name "trio" under compound ternary form.)
Changing metre mid-piece
When the metre changes partway through:
| Practice | Note |
|---|---|
| write the new signature at the start of the new bar | the standard |
| sometimes mark it at the end of the preceding system | gives the performer warning |
| a change for a single bar | common in irregular metres and folk music |
The third row matters: much folk music and many twentieth-century works change metre frequently (3/4 in one bar, 5/8 in the next), so the page shows a run of signatures and the reader must confirm every bar.
Writing compound and irregular metres
| Type | Convention |
|---|---|
| simple | 3/4, 4/4 |
| compound | 6/8, 9/8 (each beat divided in three, see [[concept:simple-compound-meter |
| irregular | often written 3+2/8 or 5/8, with beaming to show the grouping |
The key to irregular metres: the signature alone does not tell you the grouping (5/8 may be 3+2 or 2+3), so the composer either writes 3+2/8 or draws the grouping with beams (see "beaming draws the beats" under note values).
So "writing a time signature" is not merely typesetting — it carries the job of making the metrical structure clear.
Diagram: fixed order and the two letter signs
Listen: four beats against two
C (4/4) and ¢ (2/2) differ in both numerator and denominator — use rhythm to compare a four-beat cycle with a two-beat one and hear the larger beat unit (more flowing). This complements the demonstration under metre.
Common misconceptions
- "C is short for common time." It descends from medieval mensural signs (imperfect time); "common time" is
- "¢ and C are the same metre." 2/2 and 4/4 differ:
¢takes the half note as the beat and feels more - "5/8 tells you how to count." It does not: it may be 3+2 or 2+3, and **
3+2/8or the beaming must settle - "A signature is written once." Frequent changes are common (folk music, twentieth-century works), so **confirm
a later folk explanation, not the etymology.
flowing.
it**.
every bar**. :::
Listen in the library
All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).
Sources
- 拍号写在谱号与调号之后、第一小节之前；中途更换写在新小节开头，为记谱法通则
- C 与 ¢ 记号的历史来源（中世纪记谱符号）及其与现代 4/4、2/2 的对应，为音乐史与记谱法通行记载
Used for fact-checking only; all prose is original.