The "over" was a typo for "other" (hope that was obvious!). But that primarily refers to the pop/rock/folk genres. One point I'd agree on is that it will take longer for AI technology to produce a satisfying simulation of the human singing voice than it will for purely instrumental music. In fact despite the leaps and bounds in speech synthesis I've yet to hear any sort of convincing demonstration of synthesized singing. But I can't see why there's any real reason it won't happen sooner or later.