The derivation of [jū]

I now turn to the [jū] sequence of sounds and the related vowels [ū], [Λ] and [ʊ], a second area of English phonology which has occasioned abstract analyses, to see whether [jū] is also amenable to a more concrete reinterpretation. Some sample words with [jū], [ū], [Λ], [ʊ] and the [jū] ~ [Λ] alternation are shown in (3.22) and (3.23).

The main problems raised by [jū], [ū], [Λ] and [ʊ] for a phonological description of RP and GenAm are the following:

1. What is the status of the [j] glide which appears before [ū]?

2. How can we capture the fact that [j] appears predominantly before [ū], but not before every instance of this vowel?

3. What are the most appropriate underlying vowels for [jū], [ū], [Λ] and [ʊ]?

I shall first outline the answers given by Chomsky and Halle (1968), Halle (1977), Rubach (1984) and Halle and Mohanan (1985), then offer an alternative account.