Q:

How would you describe a singers voice?

I am looking for a single word, most likely an adjective, to describe a voice like Dolly Parton's voice in the song Go Tell It On the Mountains. The first adjective that comes to my mind is "sheepish" but this has a negative connotation. Maybe vibrating? Does anyone have a better word choice?
Example sentence:
The [sheepish] voice of the singer seduced the audience.
Again, I am looking for a word that does not have a negative connotation to describe a singer's voice similar to Dolly Parton's in the song.

A:

Ms. Parton uses quite a lot of vibrato, which Merriam-Webster describes as

a slightly tremulous effect imparted to vocal or instrumental tone for
  added warmth and expressiveness by slight and rapid variations in
  pitch

So tremulous or any of its synonyms (shaking, vibrating) would work.

