The conventional view of quantitative metres in medieval Hispano-Hebrew poetry confuses vowels and syllables. This is because it was syllable structure, rather than vowel typology, that produced the quantitative oppositions. Vocalic shewa was not a furtive but a regular short vowel; its syllable was light because it was not closed by a consonant. Heavy syllables were formed by closing consonants, replaceable by a long vowel, as in Arabic and other languages. Arabic metres could be used in Hebrew with no modification of their phonological basis. However, the quantitative prosody of Arabic poetry was the same as in Quranic recitation, whereas its application to Hebrew contradicted the accentual prosody of the Bible. This appears to be the reason for the controversy surrounding the introduction of Arabic metrics into Hebrew poetry. Quantitative metres require only the focus on the articulatory structures to become audible. Musical durations and accents can corroborate the metre, but they can also be non-related without compromising metre perception.