Antiharmony is the case when a stem with one or more vowels of the same phonetic features (which plays role in harmony) can be followed by a suffix with one or more vowels with the opposite feature. Antiharmony is typical for neutral vowels, that is for those, which can follow vowels belonging to any of the harmonic classes (and, as a consequence, they do not belong to any of the harmonic classes).

Finnish

Antiharmony is very exceptional in inflectional morphology, it is restricted to the forms /mer-tɑ/ ‘sea-PART’ and /ver-tɑ/ ‘blood-PART’.  However, it is much more general in derivation, especially when the suffix vowel is rounded.

Hungarian F/B harmony

Antiharmonic stems containing one /i(ː)/ are not rare, e.g. all the verbs with  /iː/ with  but /t͡ʃiːp/ ‘pinch; nip’ are antiharmonic. However, stems containing two or more vowels /i(ː)/ are never antiharmonic, except for the cases when a back vowel is deleted from the stem before a suffix: /ʃim-iːt/ ‘smooth; level; plane; even (v)’ from /ʃimɒ/ ‘smooth; even; plain (adj.)’; or when a stem without a free allomorph is antiharmonic itself: /viʃ-iːt/ ‘shriek; scream; shrill; squeal’ (cf. /viʃ-ong/ ‘shriek; scream; shrill; squeal (freq.)’. Antiharmonic stems with /eː/ are exceptional: /t͡seːl/ ‘aim, goal, purpose’, in addition, some stems can be antiharmonic due to the deletion of a back vowel: /beːniːt/ ‘paralyse’ from /beːnɒ/ ‘lame’.  Antiharmonic stems with /ɛ/ are even more exceptional: there are three examples, in which /ɛ/ freely alternates with /ɑː/. In the case of  /ʃvɛjt͡s-bɛn/ ~ /ʃvɛjt͡s-bɒn/ ~ /ʃvɑːjt͡s-bɒn/ ‘Switzerland-INE’, the stem forms with /ɛ/ are substandard. In the cases of  /ʃpɛjz-bɛn/ ~ /ʃpɛjz-bɒn/ ~ /ʃpɑːjz-bɒn/ ‘pantry-INE’ and /ʃlɛjm-bɛn/ ~ /ʃlɛjm-bɒn/ ~ /ʃlɑːjm-bɒn/ ‘phlegm-INE’, all the forms are nonstandard. In addition, there is one word, which is antiharmonic completely exceptionally: /dɛreːk-bɒn/ ‘waist-INE’, /dɛrɛk-ɒ/ ‘waist-3SG’. Beside these, another bisyllabic stem containing unrounded front vowels is exceptionaly for historical reasons: /feːrfi/ ‘man, male’ is historically a compound the second constituent of which is the monosyllabic /fi/ ‘son, boy’, which is antiharmonic (nowadays /feːrfi/ is vacillating between front and back suffixes at least when those begin with a consonant).

Nganasan quasi-rounding harmony

Stems containing any of the harmonic vowels can be antiharmonic. In the case of the neutral vowel /ə/, it is also difficult to decide which kind of suffixation is antiharmonic: although it is an unrounded vowel, the number of stems containing no other vowel but /ə/ and taking suffixes belonging to one harmonic class or to the other is approximately equal.