Native American languages, such as Cheyenne and Totonac, contrast voiced and devoiced vowels. Vowels are devoiced in whispered speech. In Japanese and in Quebec French, vowels that are between voiceless consonants are often devoiced. Modal voice, creaky voice, and breathy voice (murmured vowels) are phonation types that are used contrastively in some languages. Often, they co-occur with tone or stress distinctions; in the Mon language, vowels pronounced in the high tone are also produced with creaky voice. In such cases, it can be unclear whether it is the tone, the voicing type, or the pairing of the two that is being used for phonemic contrast. The combination of phonetic cues (phonation, tone, stress) is known as register or register complex. Tenseness Tenseness is used to describe the opposition of tense vowels vs. lax vowels. This opposition has traditionally been thought to be a result of greater muscular tension, though phonetic experiments have repeatedly failed to show this. Unlike the other features of vowel quality, tenseness is only applicable to the few languages that have this opposition (mainly Germanic languages, e.g. English), whereas the vowels of the other languages (e.g. Spanish) cannot be described with respect to tenseness in any meaningful way. One may distinguish the English tense vs. lax vowels roughly, with its spelling. Tense vowels usually occur in words with the final silent e, as in mate. Lax vowels occur in words without the silent e, such as mat. In American English, lax vowels do not appear in stressed open syllables. In traditional grammar, long vowels vs. short vowels are more commonly used, compared to tense and lax. The two sets of terms are used interchangeably by some because the features are concomitant in some varieties of English. In most Germanic languages, lax vowels can only occur in closed syllables. Therefore, they are also known as checked vowels, whereas the tense vowels are called free vowels since they can occur in any kind of syllable. Tongue root position Advanced tongue root (ATR) is a feature common across much of Africa, the Pacific Northwest, and scattered other languages such as Modern Mongolian. The contrast between advanced and retracted tongue root resembles the tense-lax contrast acoustically, but they are articulated differently. Those vowels involve noticeable tension in the vocal tract. Secondary narrowings in the vocal tract Pharyngealized vowels occur in some languages like Sedang and the Tungusic languages. Pharyngealisation is similar