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