The two numbers stacked right after the key signature are the time signature. They tell
you how the bar is built.
The top number: how many beats in a bar.
The bottom number: which note value counts as one beat. 4 means the quarter note;
8 means the eighth note; 2 means the half note.
So 3/4 is "three quarter-note beats to a bar", 2/4 is "two", 4/4 is "four".
The metre is an accent pattern
A time signature isn't just arithmetic — it tells you where the music leans.
2/4 — a march. Strong–weak. "One-two, one-two."
3/4 — a waltz. Strong–weak–weak. "One-two-three."
4/4 — strong–weak–medium–weak. Beat 1 is heaviest, beat 3 has a smaller lift.
120 bpm
3/4 — three beats a bar. Count '1 2 3, 1 2 3' and lean on every 'one'. Let 'two' and 'three' fall away lighter. That lean is the waltz.
100 bpm
4/4 — four beats. Beat 1 is the heaviest, beat 3 gets a lighter lift, 2 and 4 are the weak beats. Feel STRONG–weak–medium–weak.
Count the bar before you play
100 bpm
A 3/4 line. Work out the count for each bar — remember, only three beats each — then reveal.
Spot the wrong bar
92 bpm
This is 4/4 — four beats a bar. One bar is short. Find it, then reveal. (The middle bar has only three beats.)
Name the metre of a tune
Twinkle, Twinkle goes "Twin-kle twin-kle lit-tle star" — four steady beats
to a line, so it's in 4/4. A waltz like Amazing Grace swings in threes — 3/4.
Yankee Doodle marches in twos — 2/4.
The usual mistake
Reading the bottom number as "how many" of something. It's not a count — it's a kind of
note. "4" on the bottom always means the quarter note is the beat, whatever the top number
says. And: ignoring the metre's accent and playing every beat the same weight, so a waltz
comes out flat.