Here's my poem using "ululate." It's a working draft but I'm printing it here in thanks for the amazing response to my original query.

Suite for One Voice

Some evenings my single alto notes
rise straight up
like a mockingbird
before it plunges into Mozart.

I want to sing two-part inventions
in one voice
from a deep place within me.
Those unaccompanied notes to intercept

others a third higher
plaiting a sublime overlay
like strands of Sunday glossolalia
or a Tuvan monk's glottal hum

ululating from his Siberian village
into fog over the Farallones.