Music theorists have long been aware that different levels of beat are often simultaneously available to the listener. Harald Krebs (1999) uses the term “metrical layers” to describe this phenomenon. In the normal case, metrical layers nest neatly insideone another; they are metrically consonant with each other. This occurs, for example, in Pachelbel’s Canonas the prevailing note-values are repeatedly halved. Figure 3.1 shows this nesting relationship between layers. There is no need for a separate micropulse layer because the layers are metrically consonant: both eighth notes and quarter notes can be expressed as groupings of sixteenth notes.