Metric modulation
In music, metric modulation is a change in pulse rate (tempo) and/or pulse grouping (subdivision) that is derived from a note value or grouping heard before the change. Examples of metric modulation may include changes in time signature across an unchanging tempo, but the concept applies more specifically to shifts from one time signature/tempo (metre) to another, wherein a note value from the first is made equivalent to a note value in the second, like a pivot or bridge.