Singapore English consonant clusters undergo phonological processes that exhibit variation and opacity. Quantitative evidence shows that these patterns are genuine and systematic. Two main conclusions emerge. First, a small set of phonological constraints yields a typological structure (T-order) that captures the quantitative patterns, independently of specific assumptions about how the grammar represents variation. Second, the evidence is consistent with the hypothesis that phonological opacity has only one source: the interleaving of phonology and morphology.