Lesson 6: Time Signatures

Imagine trying to read a book with no spaces between the words and no punctuation. That is what music would be like without time signatures and bar lines. A time signature is the pair of numbers at the start of a piece that tells the player how the beats are organised. It looks like a fraction, but it is not one — the two numbers have separate jobs.

The top number tells you how many beats there are in each bar (also called a measure). The bottom number tells you what kind of note gets one beat: 2 means a minim, 4 means a crotchet, 8 means a quaver, and 16 means a semiquaver. So 4/4 means four crotchet beats per bar; 3/4 means three crotchet beats per bar; 2/4 means two crotchet beats per bar; and 6/8 means six quaver beats per bar. The bottom number works because it is the denominator of the note's fraction of a semibreve: a crotchet is a quarter of a semibreve, so it is "4"; a quaver is an eighth, so it is "8".

The Common Time Signatures

4/4, also called common time and sometimes written as a "C", is by far the most used time signature in Western music. Four steady beats per bar suit marches, pop songs, rock and most classical dances. 3/4 gives three beats per bar and a lilting, swaying feel: waltzes are in 3/4, with a strong first beat followed by two lighter ones — ONE-two-three, ONE-two-three. 2/4 has two beats per bar and a brisk, marching feel. 6/8 is different again: six quaver beats per bar, usually felt as two groups of three — ONE-two-three-FOUR-five-six — giving a rolling, lilting motion heard in jigs, barcarolles and many folk songs.

The first beat of every bar is the strongest. In 4/4, beat 1 is strongest, beat 3 is the next strongest, and beats 2 and 4 are weaker. This pattern of strong and weak beats is called the metre, and it is what makes listeners tap their feet: they are feeling the regular return of the strong beat. A time signature does not set the speed of the music — that is the job of the tempo marking — it only sets how the beats are grouped.

Simple and Compound Time

Time signatures fall into two families. In simple time, each beat divides into two: 2/4, 3/4 and 4/4 are simple, because each crotchet beat splits into two quavers. In compound time, each beat divides into three: 6/8, 9/8 and 12/8 are compound, because each dotted-crotchet beat splits into three quavers. You can spot compound time from the top number — 6, 9 and 12 — while simple time has 2, 3 or 4 at the top. A time signature with 2, 3 or 4 beats in the bar is also named by its count: two beats is duple, three is triple, four is quadruple. So 3/4 is simple triple time, and 6/8 is compound duple time. Knowing the family tells a musician at a glance how to feel the pulse and how to group the notes.

Unusual Time Signatures

Most music uses 2/4, 3/4, 4/4 or 6/8, but composers sometimes use more unusual time signatures for special effects. Dave Brubeck's famous jazz piece "Take Five" is in 5/4 — five beats per bar, usually felt as a group of three followed by a group of two (ONE-two-three-FOUR-five). The opening of Pink Floyd's "Money" is in 7/4, which feels lopsided and restless, matching the song's theme. Balkan folk music uses time signatures like 7/8 and 11/8, with the beats grouped unevenly — for example 2+2+3 — giving the dances their distinctive lilt. Some pieces change time signature every bar, which keeps the listener slightly off balance on purpose. There is also cut time (alla breve), written as a "C" with a line through it: it means 2/2, two minim beats per bar, and it is used for fast marches and orchestral music where counting four quick beats would be unnecessarily busy. The principle is always the same whatever the numbers: the top number counts the beats, the bottom number names the beat, and the first beat is the strongest.