28 Having completed our survey of three important proposals for tone structure, we
now turn to various theoretical approaches to three tonal processes: spreading, downstep, and upstep.
3.4 Tone spreading
One very common tonal process is spreading, in which a tone from one morpheme or TBU spreads to another adjacent TBU Yip 2002:9-10. In autosegmental
representations, including all three models discussed above, this is represented as follows Snider 1999:10-12:
9
What exactly spreads depends on the specific model of tone features and geometry being used. Oftentimes spreading results in the delinking of a tone already associated to the
TBU affected by spreading Snider 1999:11:
10
In Optimality Theory, there is no exact equivalent to spreading rules and several different approaches have been used in analyses of spreading. McCarthy 2010 gives a
good overview of the two major approaches: A
LIGN
constraints and A
GREE
constraints.
29 Neither of these approaches can fully account for all of the spreading phenomena in the
different languages of the world, so McCarthy 2010 proposes a new approach using a S
HARE
constraint in a framework related to Optimality Theory that is called Harmonic Serialism. Like Optimality Theory, Harmonic Serialism evaluates potential candidates for
the phonological output according to universal constraints that are weighted differently in different languages. The difference between the two theories is that Optimality Theory
goes through one process of evaluation of candidates while in Serial Harmony, G
EN
makes only one change to the input at a time. The candidates with only one change are then evaluated and the winner is then submitted to G
EN
as the input of the next cycle. This process continues until no further changes can improve the output. While this
approach may be useful, this thesis will use a traditional parallel Optimality Theoretic approach to keep the analysis as simple as possible.
A less common approach to spreading in Optimality Theory is an E
XTEND
constraint. This constraint is used in ickꜛore’ 2 aꜜaly i of Naꜛwaꜜga. It a igꜜ
a violation for an H whose rightmost edge does not follow the rightmost edge of its TBU in the input. This approach will be discussed further in §5 where it is used in the analysis
of Mbelime.
3.5 Downstep
