The Gundecha Brothers, Umakant and Ramakant Gundecha, were iconic figures in the field of Indian classical music. They were renowned Dhrupad vocalists, a genre in Hindustani classical music, known to be the oldest existing form of north Indian classical music (Hindustani classical music). Therefore, Option 1 is correct.

As for the remaining options:

Option 2 suggests they were Kathak dancers, but this isn`t accurate. Kathak is a precise and intricately expressive dance form, which is not the field the Gundecha brothers were known for.

Option 3 points to them being Sarod maestros. However, a Sarod is a stringed instrument used in Indian classical music which they did not specialize in.

Option 4 implies that they were Tabla players. Although the Tabla, a percussion instrument, is essential in Indian classical music, it was not the primary focus of the Gundecha brothers` work.

Therefore, options 2, 3, and 4 are incorrect, solidifying that the correct answer is Option 1, Dhrupad vocalists.