Rhythm in Bidayuh*

be grouped into four clusters of generally intelligible dialects: Eastern, Central, Highland and Western. In both the ultima and penult of the word, there are differences of vowel duration that create contrasting rhythm patterns. Each of the six vowels in the ultima can occur as normal or as lengthened. In the penult only four vowels occur. In most dialects there are two types of penult vowels, full and reduced. A full penult vowel is sustained and has consistent quality. Although no single phonetic feature is present in every instance of a reduced vowel, a reduced vowel frequently is brief, has lax,articulation and lengthens a following consonant. In certain environments a reduced vowel is deleted entirely. The lengthened vowels in the ultima have at least two historical sources: 1) Some lengthened vowels in Central Bidayuh have developed where a medial * of Proto Bidayuh has dropped out. 2) Some lengthened vowels descended from Proto Bidayuh lengthened vowels have developed where an Austronesian (or Malayo-Polynesian) medial laryngeal has dropped out. The full vs. reduced vowel contrast in the penult seems to be related to differences in accentual pattern in some other AN languages and apparently has developed from accentual differences at an early stage