It sounded like mattyoo

English has no settled way of writing this vowel. It appears as eu in Europe and neutral, as ew in few and stew, as u in music, as ue in cue and as ui in nuisance, and a listener choosing between them is guessing. Here the letters are eu, and they are eu because the surname is Italian rather than because of any rule about the sound. Writing yoo records what you heard with complete accuracy and still misses, which is the ordinary condition of this whole vocabulary.

A vowel pair carried in from Latin with its spelling intact.