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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
Again, since RTT is an extension of Autosegmental Phonology, the tonal processes are similar. Any level of the tonal representation can spread to a neighboring entity by linking one level below itself. In
other words, a TRN can spread to a TBU in which case both the associated register r and tonal melody T specifications would spread as well
23a. The register can spread and link to a neighboring TRN 23b or a tonal melody feature can spread 23c, likewise to a TRN. Whether or not the target of spread needs to be
an unassociated node is language specific as is whether or not delinking accompanies spreading. 23
Possible spreading routes in RTT a. TRN spread
b. Register spread c. Tone melody spread
r
x
r
y
r
x
r
y
r
x
r
y
T
x
T
y
T
x
T
y
T
x
T
y
TBU
x
TBU
y
TBU
x
TBU
y
TBU
x
TBU
y
In each of the structures in 23, the spreading feature is indicated with a dashed association line. Each of the TBUs present is fully specified as a reminder that the spread of tonal features is not necessarily
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dependent on whether or not the targeted anchor location is already specified for tone. No further processes such as delinking which often accompany spreading processes have been indicated. Below, some possible
results are demonstrated. First, complete tone spread is demonstrated in the Low Tone Spread LTS of 24. In this case,
the TBU which is targeted by the spread is unspecified for tone. 24
LTS to unassociated TBU l
L TBU
TBU The result of the spread in 24 is a tonal plateau; the two TBUs are both linked to the same Low tone and
pronounced at the same level of pitch. If the targeted TBU is already linked to a tone, a contour may appear on that TBU 25a or the
tone that is present may be delinked 25b. 25
LTS to associated TBU a. Contour tone formation
b. LTS with delinking l
h l
h L
H L
H
TBU TBU
TBU TBU
In 25a, the first TBU maintains a low tone while the second TBU which originally had a level High tone acquires a rising Low to High contour tone. In 25b, both TBUs surface with a level Low tone. The
original High tone is delinked which is represented by the two parallel bars across the association line. Similarly, when only the register feature spreads, the result is either the formation of a contour
26a or delinking of the original feature 26b which will create a level tone on that TBU as well, though the level tone may not be the same as the tone on the adjacent syllable.
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26 Register Spread
a. Contour formation b. Delinking
l h
l h
L H
L H
TBU TBU
TBU TBU
In 26a the low register spreads from the first TBU to the second, forming a register contour on the second TBU. The first syllable surfaces with a level Low tone while the second syllable surfaces with a Mid-high
to High rising contour tone. In 26b, the same register spreading process occurs; however, the register from the second TBU is delinked, again indicated by the two parallel bars across the original association
line. In this case, the initial TBU surfaces with a Low tone and the second TBU surfaces with a level Mid- high tone. In many languages, this low-register spreading accounts for downstep. If the second TBU is not
already specified for register, the spreading of the register can form a level tone on that syllable without the need for delinking.
The final spreading process that can occur is the spreading of a tonal feature. Again, the spreading may result in the formation of a contour, as in 27a, or delinking may produce level tones on each syllable,
as in 27b. 27
Tonal Feature Spreading a. Contour formation
b. Delinking l
h l
h L
H L
H
TBU TBU
TBU TBU
In 27a, the low tone feature spreads from the first TBU to the second and a contour is formed. In this case, the first TBU surfaces with a level Low tone and the second TBU surfaces with a Mid to High rising
contour. In 27b, the tonal feature on the second TBU is delinked after the tone melody feature spreads so a level Low tone remains on the first TBU and a level Mid is formed on the second. In both cases, the
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registers of the TBUs are not affected at all. Again, if no tonal melody is originally specified, a level tone is formed on the targeted syllable without the need for delinking.
In the process of spreading as it occurs within RTT, the entire tone can spread with all of its features, a register feature may spread or a tonal feature may spread. In each case, a level tone may result
on the targeted syllable in the case of delinking or if that syllable was not previously associated with a tone specification or a contour tone may result on the targeted syllable if multiple features for a given register
or tone remained linked to the TBU. Whether level tones or contour tones result from spread is a language specific parameter. In all of the examples provided here, spreading has been represented as occurring in a
rightward direction. While this is more common cross-linguistically Cahill 2007, it is not required; leftward spread is possible as well.
1.5.4.4 OCP Effects
