The process in which the developmental fate of a cell becomes restricted such that it will develop into a myoblast. A myoblast is a mononucleate cell type that, by fusion with other myoblasts, gives rise to the myotubes that eventually develop into skeletal muscle fibers. [ http://purl.obolibrary.org/obo/CL_0000056 GOC:dph GOC:mtg_muscle ]