What is the word for music that is both a capella and instrumental?

Question

Now, I know the terms "a capella" and "instrumental" are pretty incompatible, and to tell the truth, something like "Lyric-less" would fit better than "instrumental" in this case. Basically, I'm looking for a word that applies to songs that use the human voice more for the purposes of making notes than singing words, perhaps even imitating conventional instruments like violins or guitars (but not drums, I know the term for that: beatboxing).

For instance, I want a word that could be used (for example) in place of my made-up word "Accapellental" in this example sentence:

Smoove McGroove is a great Accapellental artist.

Answer 1

The a cappella group Naturally 7 calls this vocal play.

From their Wikipedia page*:

Naturally 7 is an American music group with a distinct a cappella style they call "vocal play," which, according to group leader Roger Thomas, is "the art of becoming an instrument using the human voice to create the sound." They simulate the sounds of an instrumental band using only their voices, mouths and distortion effects. The group was formed in 1999 in New York City. It currently consists of the Thomas brothers Roger (musical director, arranger, first baritone, rapping) and Warren (drums, guitar, third tenor), Rod Eldridge (first tenor, scratching, trumpet), Rickey Cort (fourth tenor, guitar), Dwight Stewart (second baritone, vocals, trombone), Garfield Buckley (second tenor, harmonica), and Kelvin "Kelz" Mitchel (bass guitar, trumpet).

^{_{* emphasis mine}}

Here is one of their videos where they demonstrate their skills. At the end they even include their definition.

Answer 2

Listen to this. This is obviously an instrumental piece, with the human voice one of the instruments.

"What need is there of words, when you will be able to convey everything better and more expressively than anyone could with words by your voice and interpretation?”

were words by the composer, Sergei Rachmaninoff, who composed the cited work, explaining the use of a single syllable in the voice.

Obviously, this cited work represents only one sort of voice and instrument music. Other specific types have established names. One word will probably never serve to describe the various uses of the human voice inter-playing with other instruments.

Fabricating a single word to fit all situations might be the best way to get a single word solution.
I would be interested if such a word took hold.