It isn't a genre. It's an orchestration.
That may be the case at present. However, most of the people here want to see a cappella grow in popularity and quality. In order to do that, it does need to take on the characteristics of a genre.
As such, there are competing interests at work. Any genre needs to have certain boundaries, and simultaneously to expand upon same.
I would draw an analogy to reality television. Every reality show employs producers and writers to help engineer the entertainment derived from the show. However, once the audience intuits that a show no longer reflects reality, it becomes disinterested. The very fact of it's ostensible reality makes it entertaining.
There is no way to extricate the circumstances of a cappella from its entertainment value. The moment audiences reject the idea that this constitutes vocal music, they will not be entertained, or the orchestration methodology will bleed into other genres.
Conversely, it is incumbent upon performers to compete in the marketplace of musical ideas. Just as reality shows have to compete with their stylized dramatic counterparts, a cappella needs to compete with other musical styles, including modern rock, pop, classical and jazz.
As such, it is important for groups to stake out as much territory as possible. The more broadly we can define a cappella, the more relevant and impactful this burgeoning genre will become.
Concerns about crossing the line are well founded. Lines and boundaries are crucial in terms of credibility. But those lines are also nebulous, because it's music and because there is no real precedent for this style of music.
Audiences are an adept guide as to whether a groups has crossed the line or nudged it. Nobody is going to come watch the Stanford Harmonics let computers do all the work for them.
Judging from the audience reaction to this performance, I'm guessing they'll be back for more.
