The various shakes and embellishments done to a human voice is collectively termed as gamaka in Indian Music. A Human voice can be modulated with proper training and tremendous effort.
Recently I came across a story on gamakas……..
‘Tirugnaana Sambandar was an eighth century poet and was one among the saivite saints. He was the father of carnatic music as he devised the gamaka. The instrument that accompanied the saint in his concert was yaazh or the kind of harp with one string for each note. The popular yaazh player of the time was Tiruneela kantan, who was sambandar’s regular accompanist. Once the people in the village gossiped that the voice of the singer has a magic spell that attracts the mass. This really hurt the yaazh player. He in return asked the vocalist to sing in a style that overpowers the instrument. The saint sang with lot of gamakas, for which the yaazh player could not keep pace and in a frustrated temperament he wanted to break the instrument into pieces. Then, Sambandar told him that devices like yaazh were after all human made and the human voice was gifted by the supreme god”. Thus, stressing the prominence of human voice over everything, gamaka became the soul of carnatic music
I personally feel that if gamaka is the test of skill for the singer and the instrumentalist then it is a delight for the listeners, and a raaga without gamaka can be compared to a flower without fragrance.