Stiff voice
The term stiff voice describes the pronunciation of consonants or vowels with a glottal opening narrower, and the vocal folds stiffer, than occurs in modal voice. Although there is no specific International [Phonetic Alphabet|IPA] diacritic for stiff voice, the voicing diacritic may be used in conjunction with the symbol for a voiced consonant. In Bru, for example, stiff-voiced vowels have tenseness in the glottis and pharynx without going so far as to be creaky voiced, whereas slack-voiced vowels are lax in the glottis without going so far as to be breathy voice.
One language with stiff voice is Thai:
Javanese contrasts stiff and slack voiced bilabial, dental, retroflex, and velar stops.
Mpi contrasts modals and stiff voice in its vowels. This is not register: for each of the six Mpi tones, a word may have either a modal or stiff-voiced vowel. For example, low tone contrasts and .