The units that encode stress, however, are abstract organizations of“beats”notated as a“metrical grid”ofxs. Eachx
in the botto mline stands for a metrical position; thexsabove the mindicate relative degrees of stress. In (3), for
instance, thefirst position has higher stress than the unstressed second position, and the third position has higher
stress than either of thefirst two.
(3)
x
xxx
xxxxxxxThe basic point of autosegmental phonology is that the metrical grid is notderivedfro msyllabic structure. Rather, it is
governed by an independent set of principles that determine what metrical configurations are possible. These
“formation rules”describe (or“license”or“generate”—choose your favorite term) a sequence of abstract positions
givenby the lowest row ofxs, to each of which is assigned a certain degree of stress. An important aspect of this little
“subgrammar”is that it sets a priority—though not an absolute requirement—on grids: they should have alternating
stressed and unstressed beats at all levels. This priority can be stated roughly as (4).
(4)
At any layer of the grid,
prefer x x (alternating
stress)
xxx
to x x (stress clash)
xxThus grid (3) is preferred to (5a), which has stress clash in the middle layer, and to (5b), which has stress clash in the
top layer (circled elements).
The syllabic and metrical structures, then, are made of different sorts of units with different combinatorial
properties—i.e. different formation rules. Since language has both kinds of structure, the structures must be matched
up. The