In many musical textures, several sonic “levels” of activity can be perceived. These levels can be separated in several ways; for example, a contrapuntal piece on one instrument might yield a sense of several different streams of activity, while timbral differences between instruments in a multi-instrument work might yield a similar effect. The coherence of the meter between these two levels leads to metric consonance and/or dissonance.
Metric consonance occurs when every pulse in the meter of the “higher” level is also a pulse in the meter of the “lower” level. The result is that both levels sound as if they are in the same, well-formed meter.
Metric dissonance, on the other hand, exists when the pulses on the two levels do not always occur together, either because one level’s meter is shifted from the other’s by a constant interval or because the number of beats in one metric pattern is not an integer multiple of the number of beats in the other metric pattern.