Which Nilo-Saharan languages use vowel harmony?

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Nilo-Saharan languages Distribution of the Nilo-Saharan languages.

Within the Nilo-Saharan languages, vowel harmony is a prominent areal feature found in several specific groups.1

Languages that utilize this feature include:

Central Sudanic languages1
Nilotic languages (part of the Eastern Sudanic group)1
Surmic languages (part of the Eastern Sudanic group)1

In these languages, vowel harmony restricts the co-occurrence of vowels within a word based on two harmonic sets, which are distinguished by the position of the tongue root (advanced versus retracted). In certain Western Nilotic languages, such as Dinka, this contrast has further evolved into a distinction between breathy and creaky voice qualities.1