[nq:1]i'm certain that: active: "x sang y" passive: "y was sung by x" are correct, and that "y was sang by x", sounds horrible; but is it 'incorrect'? Google counts: "sang by" 16900 "sung by" 485000[/nq] Yes, it's incorrect, but the form "I've sang"/"I've went"/"I've ate" etc. is widely heard among the under-educated, and is so common in some areas (I've mentioned Scotland and NE England before) that I'd consider it to be part of the dialect of those areas.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.