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language, the Mid tone is expected to form a natural class with the Low tone both of which will trigger downstep of the High tone.
The four levels of tone as described in RTT have four distinct phonological representations. In some languages, like Soyaltepec Mazatec, all four levels occur lexically. In other languages only three
lexical levels of tone occur, but the phonological definitions are still relevant and helpful in explaining the difference between the occurrence patterns of downstep between the two languages such as the
hypothetical Language A and Language B described above. For the purposes of this dissertation, it is important to remember that each of the four levels of tone is specified for either h or l register and H or L
tone, and these features are what define the phonological activity of the tones.
1.5.4.2 RTT Representations
In this section, I illustrate the autosegmental representations of tonal plateaus
22
and floating tones as represented in RTT. Contour tones were already addressed above in
§1.5.3.2. First, plateaus in RTT can be either complete or partial plateaus. 20 demonstrates a complete
tonal plateau in which two TBUs are attached to the same TRN, and a level High tone is expressed on each. 20
Tonal Plateau – the representation of a disyllabic H H word h
Register Tier H
Tonal Tier TRN
TBU TBU
In this example, both tonal features are shared by each TBU. Partial plateaus are also possible in which only one of the two tonal features is the same. In this case, the tone is not the same on the two syllables. A
plateau can occur between adjacent register levels 21a or adjacent tonal levels 21b.
22
Recall that a plateau occurs when the same feature occurs on more than one syllable in succession.
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21 Partial Plateaus
a. Register Plateau – H M
2
b. Tonal Melody Plateau – H M
1
h RT
h l
RT H
L TT
H TT
TRN TRN
TBU TBU
TBU TBU
The diagram in 21a represents a High tone H h on the first TBU followed by a Mid tone L h on the second TBU. The register is the same, h, for each tone; however, the tonal melody changes from H to L. In
21b, the tonal melody on each syllable is the same, H; but, the register changes from h to l. This represents a High tone H h on the first TBU and a Mid-high tone H l on the second TBU.
Second, floating elements may be represented in RTT. The entire tone could float 22a, a register feature could float 22b, or a tonal feature could float 22c. There are two ways to indicate floating
elements in RTT. First, when two tonal features are present but not associated to a TBU, the features are linked to a TRN as in 22a, but the TRN is not linked to the TBU. The absence of the association line
indicates the floating nature of the tonal element. In 22b and c floating elements are circled which is the more traditional representation of a floating element. This method is only possible when there is only one
feature which is floating. 22
Floating elements a. Floating tone
b. Floating register c. Floating tonal feature
l h
h l
l L
H L
L H
TBU TBU
TBU In each of the diagrams in 22 there is a linked Low tone and a floating high element. The linked tones are
placed purely for reference. I have altered the order of the floating elements in relation to the linked elements as a reminder that floating elements may occur to the right or the left of a given linked element,
e.g.: a floating tone may occur as a prefix or a suffix, it may mark the beginning or the end of a phrase, or it may be the result of a deleted first syllable or a deleted final syllable. The situation in 22a in which a
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TRN is floating is often the result of segmental deletion. Because of the phenomenon of tonal stability, a fully specified tone which was previously linked to a segment may remain after the segment is deleted
leaving the tone unattached to a TBU. In many languages, floating tones can also be part of an underlying lexical representation. In 22b, there is a floating high register and in 22c there is a floating high tonal
feature. A floating tone may attach to the surface element to its right or to its left, or it may remain floating and make its presence known by influencing the adjacent elements through downstep, upstep or through the
prevention of expected OCP violations. The directionality of floating tone attachment is not only language specific, but in some cases is morpheme specific as we will see below in Chapter 5. A floating tone may be
part of an underlying representation of a morpheme or it may be the entire underlying representation in the case of grammatical tones. For example, the case of a border tone representing the edge of a phrase is often
a floating low register feature.
1.5.4.3 Spreading
