Opposite of wailing to describe how a cello sounds

I'm looking for a word to nicely describe how a cello sounds, and I think that an opposite of wailing might be a good description.

The definition for wail describes a high-pitched tone:

Wail

1 A prolonged high-pitched cry of pain, grief, or anger.

So what would be the word for the same description, except it's a bass (or just low-pitched) tone?

The purpose is preparing subtitles for a music video which has cello playing, so it would be something like:

[Cello playing]

(But I want to replace "playing" with the cello sound word, in verb form)

Solution 1:

A low-pitch corollary to wail is moan: prolonged, primarily associated with grief or pain but can also have a counter-intuitive positive connotation ("a moan of pleasure").

Solution 2:

I think that if you choose a verb other than playing, it should also reflect how and what the cello is playing. I would describe the cello in the clip more as droning or humming than low-pitched wailing. These verbs are also more neutral in connotation and perhaps a better fit for the mood being created.

drone (v.)

To emit a continuous steady deep humming or buzzing sound, esp. a continuous musical note of low pitch; to hum or buzz, like a bee or a bagpipe. OED

The wind in the leaves hums like the violins singing; the clouds scud across a quarter moon like the mellow drone of the cello. Elaine Alphin; Simon Says

While the simple duple meter is maintained in the drone of the cello , the Indian theme uses a combination of three quarter notes , or a half note and quarter note per ... Bernadette Kopp; The Twelve-tone Techniques of Adolph Weiss

The instrumentalists took their places, checked their scores, and emitted a drone of notes, moving first from the low-end registers of cello and bass to the violins and then to the winds, like a game of sonic tag, until all the instruments were on the same wavelength.
Eric Siblin; The Cello Suites