in 1855 (right column), along with the corresponding Lepsius letters (center). In 1875, if not earlier, Wilhelm Bleek created or adopted the letter for
bilabial clicks. It would be used more extensively by
Lucy Lloyd in 1911 and added to the IPA
in 1976.
Clement Doke expanded on Jones' letters in 1923. Based on an empirically informed conception of the nature of click consonants, he analyzed voiced and nasal clicks as separate consonants, much as the voiced plosives and nasals are considered separate consonants from the voiceless plosives , and so he created letters for voiced and nasal clicks. (Like other researchers, Doke did not use the palatal click letter from the IPA. Jones had called it "velar", and people took it as having that value rather than its intended one.) Doke was the first to report
retroflex clicks, and created letters for them as well.
Douglas Beach would publish a somewhat similar system in his phonetic description of
Khoekhoe. Because Khoekhoe had no voiced clicks, he only created new letters for the four nasal clicks. Like Doke, he didn't use Jones' "velar" click letter, but created one of his own, , based on the Lepsius letter modified to better fit the design of the IPA. The
African reference alphabet proposal has apparently never been used, while the
Linguasphere and
Lingvarium transcriptions are typewriter substitutions specific to those institutions. Besides the difference in letter shape (variations on a
pipe for Lepsius, modifications of Latin letters for Jones), there was a conceptual difference between them and Doke or Beach: Lepsius used one letter as the base for all click consonants of the same
place of articulation (called the 'influx'), and added a second letter or diacritic for the
manner of articulation (called the 'efflux'), treating them as two distinct sounds (the click proper and its accompaniment), whereas Doke used a separate letter for each
tenuis,
voiced, and
nasal click, treating each as a distinct consonant, following the example of the Latin alphabet, where the voiced and nasal
occlusives also treated as distinct consonants (
p b m, t d n, c j ñ, k g ŋ). Doke's nasal-click letters were based on the letter , continuing the pattern of the pulmonic nasal consonants . For example, the letters for the palatal and retroflex clicks are ⟨ŋ⟩ ⟨ɲ⟩ with a curl on their free leg: ⟨⟩ ⟨⟩. The voiced-click letters are more individuated, a couple were simply inverted versions of the tenuis-click letters. The tenuis–voiced pairs were dental (the letter had
not yet been added to the IPA for the
voiced velar fricative), alveolar , retroflex , palatal and lateral . A proposal to add Doke's letters to
Unicode was not approved. File:ʖhapopen ʇʔoas.png|The Nama name
ǁhapopen ǀoas (
ʖhapopen ʇʔoas), from Beach's phonology. File:Khoekhoe words ǂae ǂʔui.png|The Khoekhoe word
ǂgaeǂui (
𝼋ae-𝼋ʔui), illustrating Beach's distinctive form of the letter
ǂ. File:Khoekhoe ǁnau.png|The Khoekhoe word
ǁnau (
𝼎au), illustrating the curled tail Beach used to indicate
nasal clicks. Beach wrote on
Khoekhoe and so had no need for letters for the voiced clicks; he created letters for nasal clicks by adding a curl to the bottom of the tenuis-click letters: . Doke and Beach both wrote aspirated clicks with an
h, , and the
glottalized nasal clicks as an oral click with a glottal stop, . Beach also wrote the affricate contour clicks with an
x, . The only other scripts to have letters for clicks are
N'ko in Mali and
Luo script in Botswana, which include them for paralexical use, and the experimental
Ditema tsa Dinoko script, which uses them lexically. ==Transcribing voiced and nasal clicks, and the velar–uvular distinction==