Time signatures

A time signature is two numbers at the start of a piece, stacked like a fraction but not one.

• Top number — how many beats in a bar.
• Bottom number — which note value counts as one beat.

The bottom number is written as a denominator: 4 means quarter note, 8 means eighth note, 2 means half note.

So 4/4 is four quarter notes per bar. 3/4 is three. 6/8 is six eighth notes.

The common ones

Simple vs compound time

This is the distinction that matters and the one most explanations skip.

In simple time, each beat divides into two. 4/4, 3/4 and 2/4 are all simple.

In compound time, each beat divides into three. 6/8, 9/8 and 12/8 are compound.

Which is why 6/8 is not "3/4 played faster". In 6/8 you feel two beats per bar, each a dotted quarter, each split into three eighths. In 3/4 you feel three beats, each a quarter, each split into two. The bar contains six eighth notes either way — the grouping is completely different, and so is the music.

Count them out loud and you can hear it immediately:

• 3/4 — ONE two three, ONE two three
• 6/8 — ONE two three FOUR five six

Where the accent falls

Every meter has a natural stress pattern, and this is most of what a time signature actually communicates:

• 4/4 — strong, weak, medium, weak
• 3/4 — strong, weak, weak
• 6/8 — strong, weak, weak, medium, weak, weak

Composers play against these constantly. Syncopation is only interesting because there is an expected accent to contradict.

Odd and changing meters

5/4, 7/8 and similar are usually felt as uneven groupings — 7/8 as 3+2+2 or 2+2+3, for instance. Some pieces change signature bar to bar. Neither is exotic; both follow the same two rules from the top of this page.