What is this sound called?
troll (v.)
To troll a song, to roll it out with rise and fall of the voice [probably the equivalent of Swiss tralallen, to sound notes without words—from a representation of the notes by the syllables tra-la-la]. United Editors Encyclopedia and Dictionary (1907)
To troll or trowl a song may be to roll it out with rise and fall of voice, but it is more probably the equivalent of G. trallen, trallern, trällern, Swiss trallen, tralallen, trallallen, to sing a tune, to sound notes without words; from a representation of the notes by the syllables tra-la-la. Dictionary of English Etymology Vol. 3 (1865)
(Used with object)
To sing or utter in a full, rolling voice.(Used without object)
To sing with a full, rolling voice; give forth full, rolling tones.
To be uttered or sounded in such tones. dictionary.com
When success had finally crowned his efforts, a sudden impulse of boyish exuberance caused him to troll out an old Tyrolese Alpine song, "Tra, la, la, la, la, la, la, tra, la la, tra, la la!" with a peculiar flute-like execution. Alica McAlilly; Terra Cotta. (1903)
"...How am I ever to speak to her to-day, if I fill my head with such sickly rubbish? Tra-la-la-la-lira! A fine day for a walk. I must go early and get to business. Somehow or other the thing must be managed. Tra-la-la-la-la."
Cheerfully trolling a Tyrolean scrap, he set to work on his breakfast... Lucy B. Walford; Mr. Smith, Vol. 2 (1876)
Sometimes he twirled a great quarterstaff which he held in his hands, and again he would start whistling, or begin trolling a song at the top of a loud voice. Henry Gilbert; Robin Hood
Think I perchance to sing or troll a tune
For medicine against sleep, the music soon Aeschylus; Agamemnon
The saloons (there are five) no longer feature a "stink of stale beer and thick voices bellowing pidgin German or trolling out dirty songs—vice gone feeble and unenterprising." Life, June 23, 1947
Try ululate which Merriam-Webster (online) defines as an intransitive verb meaning
to utter a loud, usually protracted, high-pitched, rhythmical sound especially as an expression of sorrow, joy, celebration, or reverence
offering the sample usages
eight singers took to the aisle, dancing with ferocious energy as the chorus sang, ululated and clapped in an exuberant, multisensory ode to joy.
As soon as he said our mother's name, my sisters began to wail: keening, ululating cries, the Greek expression of sorrow for the dead.
From ululate we can derive the noun ululation, the -ing form of the verb ululating, etc.
I expect other reputable dictionaries offer much the same definition.