Explanation:

- Lalgudi Gopala Iyer Jayaraman was a celebrated Indian violinist known for his contributions to Carnatic music.

- He was renowned for his incredible skill on the violin, an instrument vital to the classical music tradition of South India.

- Option 1: Harmonium - While harmonium is a popular instrument in Indian music, Lalgudi Jayaraman was not known for playing it.

- Option 2: Flute - The flute is another classical instrument, but not the one associated with Lalgudi Jayaraman.

- Option 3: Mridangam - This is a percussion instrument used in South Indian music, but Lalgudi Jayaraman was not a mridangam player.

- Option 4: Violin - This is indeed the instrument for which he gained fame and that he used to elevate the status of violin in Carnatic music.