The process in which a relatively unspecialized cell acquires specialized features of a myoblast. A myoblast is a mononucleate cell type that, by fusion with other myoblasts, gives rise to the myotubes that eventually develop into striated muscle fibers. [ http://purl.obolibrary.org/obo/CL_0000056 GOC:go_curators GOC:mtg_muscle ]