Time Signatures & Meter
Beats come in bundles with a strong one in front. The two numbers at the start of a piece say how big the bundle is — and the tempo says how fast it goes.
Builds on: 1.2 Note Values & Rests
Two numbers, one bar
Listen to almost any music and the beats fall into groups: ONE two three four, ONE two three four. Each group is a bar (or measure), separated on the page by vertical bar lines, and the time signature at the start describes the group. The top number says how many beats are in each bar; the bottom number says which note value counts as one beat: 4 means a quarter note, 8 an eighth, 2 a half. So 4/4 is four quarter-note beats per bar — so common it is also written as a big C for “common time”. 3/4 is three quarter beats (the waltz), 2/4 two (the march).
Strong and weak
A bar is not just a count; it is a pattern of weight. Beat 1, the downbeat, is the strongest. In 4/4 beat 3 is a secondary accent and 2 and 4 are weak; in 3/4 there is one strong beat and two weak ones, which gives the waltz its lilt. This pattern of accents is the meter. Composers play against it constantly — a note stressed on a weak beat is a syncopation and the whole of jazz and pop leans on it — but the pattern has to exist before it can be played against.
Simple and compound
When each beat divides naturally into two (a quarter into two eighths), the meter is simple: 2/4, 3/4 and 4/4. When each beat divides into three, it is compound, and the signature counts the small notes: 6/8 has six eighths, but you feel it as two big beats each holding three eighths — ONE-and-a TWO-and-a, the swing of a jig or a barcarolle. 9/8 is three such beats, 12/8 four (the slow blues shuffle). The rule of thumb: a top number of 6, 9 or 12 means compound, feel it in threes.
Tempo: how fast the beats go
The time signature says nothing about speed. That is tempo, given as beats per minute — “♩ = 120” means 120 quarter-note beats a minute, one every half second — or, in older scores, as an Italian word:
- Largo 40–60 · very slow, broad
- Adagio 66–76 · slow, at ease
- Andante 76–108 · walking pace
- Moderato 108–120 · moderate
- Allegro 120–168 · fast, cheerful
- Presto 168–200 · very fast
Many tunes start before the first downbeat — “Happy Birthday” begins on beat 3 of a 3/4 bar (“hap-py”) and lands on beat 1 with “birth-”. That short first bar is a pickup (anacrusis), and traditionally the last bar of the piece is shortened to make up the missing beats.
The Meter Machine below plays any of four signatures at any tempo and lights the beats as they pass, big on the strong ones. Then test your inner clock with the tempo guesser.
🎼 Lab — Meter Machine
Choose a time signature and a tempo, press ▶, and watch the beats light up in turn — the strong beat big and amber, the weak ones small.
- Run 4/4 at 100 BPM and count aloud; then switch to 3/4 without stopping — feel the waltz arrive.
- Switch to 6/8: six lights, but only two of them strong. Count “ONE-and-a TWO-and-a”.
- Drag the tempo from 60 to 180 and watch the seconds-per-bar readout shrink.
🎼 Lab — Tempo Guesser
The metronome plays at a hidden tempo. Move the slider to what you think it is, then reveal — within 6 BPM counts as a musician’s ear.
- Anchor on 60 BPM (one beat a second) and 120 (two a second) and judge from there.