Processing IPA Unicode with Python

by Kris Shaffer

One of the main challenges I anticipated for this project was dealing with our phonetic data. Vocalists typically use the International Phonetic Alphabet (IPA) to guide their pronunciation while singing in a non-native language, and there are many sources of IPA transcriptions of art song texts, so it seemed like a natural place to start. However, my software coding experience has been limited to the processing of numerical data and plain text, and IPA involves a number of "special characters." I thought it would be a big challenge for my initial coding effort.

However, it turned out to be fairly simple. I write my code using the Python scripting language, which — as it turns out — offers good support for Unicode text. We also found a Unicode font designed specifically for IPA. Putting these two together has made the analysis of IPA text fairly straightforward.

First, here is a sample German poem, "Nacht und Träume," and its IPA transcription:

Heil'ge Nacht, du sinkest nieder;
Nieder wallen auch die Träume
Wie dein Licht durch die Räume,
Lieblich durch der Menschen Brust.
Die belauschen sie mit Lust;
Rufen, wenn der Tag erwacht:
Kehre wieder, heil'ge Nacht!
Holde Träume, kehret wieder!

ha:Ilgə naχt du zIŋkəst nidəʁ
nidəʁ val:lən a:ʊχ di trɔ:ymə
vi da:In montlIçt dʊɾç di ɾɔ:ymə
dʊɾç deʁ mɛnʃən ʃtIl:lɛ bɾʊst
di bɛla:ʊʃən zi mIt lʊst
ɾufən vɛn deʁ tak ɛɾvaχt
keɾɛ vidəʁ ha:Ilgə naχt
hɔldə tɾɔ:ymə keɾət vidəʁ

We began by making a plain text file containing the IPA transcription. Then we used Python's codecs framework to import the text in a usable format.

import codecs
content = [line.rstrip('\n') for line in codecs.open('NachtUndTraume.txt', encoding='utf-8')]

Analyzing the text takes a little more work, but it's still fairly simple. For example, one thing we're looking at is the relative occurrence of different vowel types, and how that changes poem-to-poem, stanza-to-stanza, line-to-line. That analysis begins with categorizing the vowels in the poem: open, open-mid, close-mid, close, neutral. To do this, we use a Python dictionary, but we have to interact with the Unicode background to make this work. Using the chart provided with the IPA Keyboard Layout, we identified the IPA designation for each character. Then we used those to setup the dictionary.

phonemeCategory = {   
'a': 'open',
u'\u0061': 'open',
'e': 'closeMid',
u'\u025b': 'openMid',
u'\u0259': 'neutral',
'i': 'close',
'I': 'open',
'o': 'closeMid',
u'\u0254': 'openMid',
u'\u00f8': 'closeMid',
u'\u0153': 'openMid',
'y': 'close',
u'\u0153': 'close',
'u': 'close',
u'\028a': 'close',
}

Note that for regular Roman characters, we can simply type the character. Only the "special characters" need the full Unicode treatment.

With this dictionary defined, we can simply ask the category of each phoneme

phonemeCategory[phoneme]

and use the usual tools to calculate probabilities, make comparisons, etc.

Once we had an IPA-friendly Unicode font, processing the IPA text became very simple.

Entering that IPA text is another story...