Sotho tonology


Notes:



Like most other Niger–Congo languages, Sesotho is a tonal language, spoken with two basic tones, high and low. The Sesotho grammatical tone system is rather complex and uses a large number of "sandhi" rules.
However, the Sesotho system is by no means the most complicated, nor even one of the more complicated. For example, there exist African grammatical tone languages with much more than just two tonemes, and the existence of breathy voiced consonants in the Nguni and other languages greatly complicates their tonology. There are also very few instances of "floating" tones, and fewer grammatical constructs indicated purely by a change in tone. The rules are generally not very dramatic either, and there is generally a very strong tendency to preserve underlying high tones.
The tone of a syllable is carried by the vowel, or the nasal, if the nasal is syllabic. The tone carried by syllabic (and, in Northern Sotho and Setswana, syllabic is left over from the elided vowel.

Tone types

Underlyingly, each syllable of every morpheme may be described as having one of two tone types: high and null. On the surface, all remaining null tones default to low and the language is therefore spoken with two contrasting tonemes.
A classic example of a nasal carrying a tone:
Names, being nouns, frequently have a tonal pattern distinct from the noun:

Allotones

In speech, the two surface tonemes may be pronounced as one of several allotones due to the influence of surrounding tones and the length of the syllable. These changes naturally occur due to the way the language is spoken, including the effect of the penultimate lengthening, but ultimately each syllable of every morpheme may be completely described as having only high and low tones.
In this and related articles, the tonemes of a word are delimited with square brackets and the specific spoken allotones are between curly braces.
Thus in all there are, at least in this analysis, eight allotones '.
Most of these allotones only appear on the final word in the phrase in moderately slow or emphasised speech. When not phrase-final, the mid, high-falling, high-mid, low-falling, and extra-low allotones are normally not heard. Bear in mind that the falling tones only occur on lengthened syllables, and if a word has irregular stress then the falling tones will not appear on the penult.
There are no rising tones. For example, ' is pronounced ' though one might have expected *'. This is a general trend among almost all Bantu languages with lengthened vowels, though languages with depressor consonants do have audible upward "swoops" on depressing syllable onsets which may be interpreted as rising allotones.
There are several cases of seemingly tonemic instances of some of these allotones. As expected, some ideophones and radical interjectives have strange tones, but relative concord has an irregular extra-high tone. The difference in relative pitch between the high tone and its extra-high allotone is less than that between the low and high tones.

Tone usage

The purpose of the tones can fall into at least one of the following categories:

Characteristic tone

Each complete Sesotho word has an inherent tone for its syllables, which, although not essential to forming correct speech, will betray a foreign accent:
Various factors mean that the tones of a word may change, but the characteristic tone in a Sesotho word is found when the word is the last in a question sentence not employing the interrogative adverb na?. In this situation, downdrift is greatly attenuated, the penultimate syllable of the sentence is short, and the tone of the last word is largely preserved.

Distinguishing/semantic tone

The most important property of tonal languages which distinguishes them from languages that merely use pitch as part of intonation is the existence of numerous tonal minimal pairs. Often, a few words may be composed of exactly the same syllables/phonemes, yet have different characteristic tones :
There are, however, several basic homophones pronounced with exactly the same tonal patterns. In these cases only the context may be used to distinguish between the different meanings.
There are instances of words being changed either through inflexion or derivation and as a result ending up sounding exactly like other words.

Grammatical tone

It regularly occurs that two otherwise similar sounding phrases may have two very different meanings mainly due to a difference in tone of one or more words or concords.
Note that when grammatical tone is used the tone of the significant word may influence the relative pitch of the rest of the phrase, although the tones of other words tend to remain intact.

Downdrift

Downdrift, where the absolute pitch of the speaker's voice is gradually decreased as the sentence continues, is a feature during natural speech. Basically, a high tone immediately following a low tone is pronounced at a slightly lower frequency than a previous high tone.
Additionally, a slightly more dramatic lowering of pitch may occur between certain syllables. In Sesotho, the downstep naturally occurs between words though there is at least one instances where the lack of downstep changes the utterance's meaning. In the following example, a grave accent indicates a low tone and an acute accent indicates a high tone.

This downdrift is greatly attenuated when the sentence is a question not using the interrogative adverb na?.

Verb tone

Sesotho verb stems fall into two categories: H stems and L stems. The difference lies in the "underlying tone" of the stem's first syllable being either high or null. When used with an object in the indicative remote future tense the verb's stem is monotonous with the underlying tone of the first syllable spread to all the following syllables.
Nouns derived from the verb stem are fossilised with the tones of the simple class 15 infinitive as appears in medial positions without a subject or object. The procedure for creating this tonal pattern is intricate and involves several [|tonal rules].
These factors may also apply in normal verbal conjugations. Adding a verbal suffix creates a new verb stem which falls in the same tone category as the original, and is subject to the same rules.
The tones of the noun prefixes of nouns derived from verbs are independent of the tones of the stem.
Some nouns derived from verbs have idiomatic tonal patterns independent of the original verb stem's tones.
Several "tonal melodies" may be assigned to certain verbal conjugations based on the desired tense, aspect, and mood. These are applied before most other rules and may be indicated by a code including the symbols H, L, B, and *.
For example, applying the "Subjunctive Melody" to the H verb stem -bona and the L verb stem -sheba results in both ke shebe tau and ke bone tau being pronounced with exactly the same tone pattern .
Another way to designate the melodies is to use a standard template of the tense in question and indicate the melody by assigning tones to specific syllables in the resultant word. So for the above example the Subjunctive Melody may be specified by putting H tones on the first syllable, the second syllable, and final syllable of the word and putting an explicit L tone on the fourth syllable —thus preventing HTD.

Tonal rules

Sesotho is a grammatical tone language; this means that words may be pronounced with varying tonal patterns depending on their particular function in a sentence. Another interpretation is that the tones of the language interact in their own intricate "tonal grammar."
In order to create certain grammatical constructs, certain tonal rules may be used to modify the underlying tones of the word to create their surface tones. The words are then spoken using the surface tones.
This system is naturally somewhat complex. Indeed, the development of autosegmental phonology was largely motivated by the need for a satisfactory theoretical framework to deal with the tonal grammars of Niger–Congo languages. This article attempts to explain certain aspects of Sesotho tonology in a rule-based autosegmental framework.
The rules presented below are almost exclusively used in constructing the verbal complex as this is the part of speech most radically affected by the tonal grammar.

About autosegmental phonology

Autosegmental phonology was motivated by the need to represent properties which seem to span several "segments" and seem to be somewhat independent of them. Underlyingly, some, but not necessarily all, of the segments of morphemes are associated with one or more properties. The segments are on one "tier" and their properties are on another, and the relationships between the two are indicated by joining them with association lines as follows:

Each of the rules changes the associations in some way. For example, High Tone Doubling causes the underlying H tone on the first syllable of the verb to also be linked to the syllable immediately to the right:

In this article, the application of several rules in succession will be indicated with the following abbreviation:

The fact that the line emanating from the second syllable is only linked on the HTD line means that this is the first time that syllable is associated with that property.

Typology

One popular classification of tonal Bantu languages broadly separates them into two group: shifting languages and spreading languages. The Sotho–Tswana languages are bounded spreading languages as they have primitive rules which directly cause underlying high tones to be associated with syllables to the right. The closely related Nguni languages, on the other hand, are unbounded shifting languages as they have primitive rules which directly cause underlying high tones to be moved syllables to the right. The following table presents an informal comparison between the tonal processes found in Sesotho and isiZulu :
In the table, a process is unbounded if there is no set limit on the number of syllables over which it may occur. Sesotho has basic bounded spread and isiZulu has basic unbounded shift. Bounded shift in Sesotho occurs as the cumulative effect of bounded right tone spread and Left Branch Delinking, while various forms of spreading may occur in isiZulu if the word is very short or has two or more underlying highs.

Some tonal rules

In dealing with verbs, the following rules may be applied at various times:High Tone Doubling causes the H tone found on the first syllable of the verb stem, or on an H toned subjectival concord, to be spread to the syllable immediately to the right. For example, :
Iterative Tone Spread causes the H tone found on the first syllable of the verb stem to be spread repeatedly to the right until the end of the verb complex. This rule is only applied in certain situations. For example, :
Right Branch Delinking is an application of the obligatory contour principle which causes an H tone spread from a subjectival concord to a verbal auxiliary infix or objectival concord immediately to the left of the verb stem to be removed if the verb stem is an H stem. For example, :
Left Branch Delinking is an application of the "obligatory" contour principle which causes the H tone on the first syllable of an H verb stem to be delinked if the stem immediately follows an H toned subjectival concord, resulting in tonal pattern. This rule is idiolectical and is not applied by all Sesotho speakers. For example, :
The Finality Restriction causes any H tones spread to the final syllable of the verb complex to be removed. This rule is not applied under all circumstances, and is never applied if the verb's stem is monosyllabic. It is also never applied when the verb is immediately followed a direct object. For example, :
Low Tone Assignment is the very last rule applied and is always applied in all circumstances. It simply assigns all unlinked segments with an L tone. For example, :

Some examples

To construct many verb forms, including many positive indicative tenses without direct objects as well as infinitives, the following rules are applied in order:
Note that the three main levels are always applied in this order, though the actual rules contained in the levels will change depending on the parts of speech, verb moods, etc. For the word o a bina the application of the rules is as follows:

The word appears on the surface with tonal pattern '.
Furthermore, the second last syllable of the word is lengthened, and the interaction of the tones as well as the penultimate lengthening results in the word being pronounced with pitch levels '.
Extending the word by one syllable :

The word appears on the surface with tonal pattern '.
The second last syllable of the word is lengthened and the interaction of the tones as well as the penultimate lengthening results in the word being pronounced with pitch levels '.