Using your voice as an instrument

What are some words that describe using one's voice as an instrument, i.e. doing certain things with the voice, not necessarily just hitting particularly challenging higher/lower registers? Things like yodeling; a yodeler is a [word], someone who is [word], someone who can [word].

Singing ability in general is called vocal technique, and a skilled vocalist has good technical ability. More specific elements of vocal technique include breath control, phonation, resonation, articulation, pitch, range, tone, flexibility, agility, and vibrato. You can write:

Yodeling is a vocal technique.
He is a technical vocalist.
She can sing technically.

Vocal techniques like yodeling and scat singing that emphasize non-lexical vocables (nonsense syllables) are sometimes called voice instrumental music. Beatboxing specifically features vocal percussion and imitation or emulation of musical instruments; the latter also features prominently in some a capella styles. Thus, if you want to emphasize the instrument-like nature of a technique or singer, you can instead follow these examples (borrowed from the linked Wikipedia articles):

Scat singing is a type of voice instrumental music.
He is a vocal percussionist.
She can emulate instrumentation.

I would use the word beatboxing. I have a friend that can do a full band while beatboxing, myself I can only do the horn section.

Beatboxing (also beatbox, beat box or b-box) is a form of vocal percussion primarily involving the art of producing drum beats, rhythm, and musical sounds using one's mouth, lips, tongue, and voice. It may also involve singing, vocal imitation of turntablism, and the simulation of horns, strings, and other musical instruments. Beatboxing today is connected with hip-hop culture, being one of "the elements", although it is not limited to hip-hop music.1[2] The term "beatboxing" is sometimes used to refer to vocal percussion in general (see vocal percussion for details).

Here is a good example.