Metre
Metre is the regular pattern of strong and weak beats. The first beat of every group is the strong beat; the others are weak beats.
The beat ticks evenly, yet we hear it in groups: the first beat of each group feels stronger. The group from one strong beat to the next is a measure, and the time signature tells how many beats it holds. In 4/4 the beats go strong, weak, weak, weak; in 3/4 strong, weak, weak; in 2/4 strong, weak.
In four, beat three is a little stronger than beats two and four — it is called relatively strong. In 6/8 the strong beats are one and four: two groups of three, which is why 6/8 feels like a metre in two.
Metre is not the same as rhythm: metre is the steady framework, rhythm the pattern of notes laid over it. In accompaniments the strong beat is often marked by a low bass note or a chord.
What it sounds like
Metre is heard as a sway: ONE, two, three for a waltz; ONE, two for a march. The strong beat pulls towards itself like the weight of a step.
Where it is taught: the studio’s interactive textbook, chapter 3, “Measures and time signatures” and chapter 14, “6/8 and the waltz pulse”.