Metre change

What it means

A metre change is the transition to a new time signature within a piece. The new marking applies from the bar before which it stands and remains in force until another follows.

The decisive question with every metre change is which note value stays the same. If the beat stays the same, only the grouping changes — four quarters become, say, three, the basic tempo stays. If, by contrast, the smallest value stays the same while the beat changes, the felt tempo changes. Composers often indicate this through a note-value equation, for instance by equating a quarter of the old bar with a dotted quarter of the new one. If such an indication is missing, it usually holds that the shared smallest note value stays constant.

In the notation

The new time signature stands after the barline, that is, at the beginning of the first bar for which it applies. At the end of the preceding line, some editions repeat it as an advance warning. If the time signature changes frequently, some editions notate it above the staff instead of within it, to keep the notation calm. A note-value equation stands above the change point.

Musical use

Isolated metre changes are found in older music at formal boundaries, for instance at the transition from a duple to a triple section. In the twentieth century, frequent, sometimes bar-by-bar change becomes a device of shaping in its own right: the music then follows the phrase instead of a fixed pattern. In the setting of prose texts, too, it serves to reflect the speech rhythm.

Performance practice

Clarify before practising which value stays the same, and write the equation over the passage if necessary. Count the last bar before the change fully out before you switch — most errors arise there, not in the new bar. Practise the change point as a short unit made of the last and first two bars. And mark, with frequent changes, the counting method in the notated text, so that you do not have to derive it anew every time.