What is "vowel system"

Usage examples of "vowel system".

But the people writing the phrasebook for the human ear are laboring under a terrible handicap, trying to transliterate from a thirty-seven-vowel system to an alphabet with only five.

I do owe many thanks to the various elven native speakers who have suggested which consonant to choose in confusing cases and who have laboured, alas often in vain, to refine my ear to the elven vowel system.

I do owe many thanks to the various Elven native speakers who have suggested which consonant to choose in confusing cases and who have labored, alas often in vain, to refine my ear to the Elven vowel system.