How beats are counted, grouped and written.
What you’ll learn in this section
- What the two numbers in a time signature actually tell you
- The difference between simple and compound time — beats that split in two vs three
- How rests, bar lines and beaming keep the beat visible on the page
Time signatures
A "time signature" is two numbers at the start of a piece. The bottom number names the unit: 4 means a crotchet, 8 means a quaver. The top number says how many of those units fill one bar.
So 4/4 means four crotchet beats per bar — the most common time signature, sometimes called "common time". 3/4 means three crotchet beats per bar — the feel of a waltz.
✔ Quick check: In 4/4, how many crotchet beats are in each bar?
The top number tells you how many beats per bar. The bottom number tells you what note gets one beat (4 = crotchet, 8 = quaver). Read top first, then bottom.
Bar lines and the anatomy of a piece
The vertical barlines divide the music into bars (also called measures), each holding the number of beats the time signature promises. They are the music's regular punctuation, making the pulse visible on the page. A double barline marks the end of a section, and a final barline (thin then thick) marks the end of the piece.
Anatomy of a short piece
Here is a four-bar phrase in 4/4. Every part of the notation has a job:
Each bar holds exactly four crotchet beats — whether filled by four crotchets, a minim and two crotchets, or a single semibreve. The counts always add up to what the time signature promises.
Double bar line = section end. Repeat signs (||: :||) mean go back. Final double bar = piece ends.
Rests — how silence is written
Every note value has a matching rest of exactly the same length, so silence obeys the same doubling system as sound. The bar must still add up: notes and rests together total what the time signature promises.
| Rest | Name | How it looks | Beats in 4/4 |
|---|---|---|---|
| Semibreve rest | hangs below the line | 4 | |
| Minim rest | sits on the line | 2 | |
| Crotchet rest | a vertical squiggle | 1 | |
| Quaver rest | slanted stem, one hook | ½ | |
| Semiquaver rest | slanted stem, two hooks | ¼ |
The two easiest to confuse are the semibreve and minim rests — both are small blocks on the middle line. Remember it this way: the semibreve rest hangs below the line (heavier, longer), and the minim rest sits on top. A dotted rest works like a dotted note: the dot adds half the rest’s own value.
Rest conventions — keeping the beat visible
Rests follow the same grouping logic as beams: they are written so that each beat can be seen at a glance. Two rules cover almost everything at this stage.
1. A rest never crosses a beat boundary. If a silence spans from the middle of one beat into the next, split it into two rests — one finishing the first beat, one starting the second — even though a single longer rest would have the same total length.
2. Complete the current subdivision first, then think bigger. Coming out of a semiquaver, first write the rest that finishes the half-beat, then whatever fills the rest of the beat. This is why a beat that goes “semiquaver, then silence, then semiquaver” uses two semiquaver rests in the middle rather than one quaver rest sitting awkwardly across the half-beat.
One special case to know: a whole bar of silence is always written with a semibreve rest, whatever the time signature — even in 3/4, where a semibreve would be too long as a note. It simply means “this bar is empty.”
Notes and rests, sharing the bar
Now that you know rests, look again at the anatomy of a piece. A bar does not have to be filled with sound — notes and rests together add up to what the time signature promises. A rest takes up its beats just as surely as a note does.
Anatomy of a short piece — with rests
The same four-bar phrase in 4/4. This time some beats are silent — but every bar still totals four:
Bar 2 is a minim of sound then a minim of silence; bar 3 places a crotchet rest among its notes. In every case the beats — sounded or silent — add up to four. That is the rule a time signature enforces.
Fill every bar so the total note + rest values equal the top number of the time signature. If the top is 4, every bar must add up to 4 crotchet beats.
Same attacks, different lengths — why rests matter
Rests are part of the rhythm, not just empty gaps. Press both rows below: the notes start at exactly the same moments — but listen to what happens between them. The top row falls silent; the bottom row keeps sounding right up to the next note.
Proof: same attacks, different lengths
Turn on both ♪ buttons: this widget plays sustained tones rather than clicks, so you can hear it — the attacks land together, but the top row is clipped and detached while the bottom row sings through. Watch the green bands tell the same story: short–gap–short versus long–short.
✔ Quick check: Half a beat of silence runs from the middle of beat 2 into the middle of beat 3. How should it be written?
Simple and compound time
In "simple time" (2/4, 3/4, 4/4) each beat divides naturally into two equal parts. In "compound time" (6/8, 9/8, 12/8) each beat divides into three. This is why 6/8 does not feel like six separate beats — the six quavers are grouped as two sets of three, giving two compound beats. A jig is in compound time; a march is in simple time.
Top number 2, 3 or 4: simple time. Top number 6, 9 or 12: compound time. In compound time the beat is always a dotted note (grouping three shorter values).
Train your ear
Even, dotted, or triplet? Press Play and name how the beat divides.
Six identical quavers. Two different metres.
Both rows below contain exactly the same six quavers at exactly the same speed. The only difference is how they are grouped — and that difference is the time signature. In 3/4 the quavers pair up into three crotchet beats; in 6/8 they bundle into two dotted-crotchet beats. Look at the beams: 2+2+2 against 3+3. Turn on both ♪ tracks and the accents (the > marks) tell your ear which world you are in.
Hear it: 3/4 vs 6/8
Accented clicks are louder and lower. Try each row alone first, then both together — same grid, different pulse.
Clap along — same quavers, two pulses
Identical six quavers underneath; the top line is where the beat is felt. Loop each and clap the top line.
✔ Quick check: In 6/8, how many quaver beats make up one felt beat?
See how simple and compound time group their beats differently — two rules, side by side.
Set a tempo, choose simple or compound feel, and hear the beat subdivisions — tap to match a song.
Beaming — the composer’s grammar
Written music follows conventions for the same reason written language has punctuation: to make the reader’s job easier. Beaming — joining quavers and shorter notes with a horizontal bar — is one of those conventions. Its purpose is to make each beat visually obvious at a glance, so the reader can track the pulse without counting individual flags. Composers treat it as a shared code, not a personal style choice.
In 4/4: beam in crotchet-sized groups (beats 1–2, beats 3–4 — never across the half-bar). In 6/8: beam all six quavers as two groups of three.
- In 4/4, do not beam across the half-bar boundary (beat 3). Quavers on beats 1–2 can beam together; quavers on beats 3–4 can beam together; but a beam must not link a note from beat 2 to a note on beat 3.
- In 3/4, you may beam across the bar freely because all three beats are of equal weight, but a single quaver is usually written with a flag rather than beamed to the next bar.
- In 6/8, beam in groups of three quavers (one dotted-crotchet beat per group). A beam of six quavers across the whole bar is acceptable; a beam of four quavers straddling the midpoint is not.
- Rests follow the same principle — use rests that fill complete beats or sub-groups, not rests that split a beat in two across a boundary.