Was born in a Sikh family of Vandar, a village in Faridkot district of the Punjab. He had a sensitive ear for music from his early childhood. His father, a pious Sikh himself, apprenticed him for religious instruction to the mahant or custodian of Gurusar (Mehraj), a historical shrine about 25 km northeast of Bathinda. The mahant was impressed by the rapid progress Gajja Singh made in learning the scriptural and other texts and by his ability to sing the sacred hymns in the folk tunes he had picked up in his native village. He arranged, through the mahant of Gurdwara Ber Sahib, Sultanpur Lodhi, to send young Gajja Singh to learn classical music under Mir Rahmat

All, the eminent court musician of Kapurthala state. One of his co-pupils was Mahbub Ali alias Bhai Buba, a direct descendant of Bhai Phiranda of Bharoana, to whom Guru Nanak had, just before setting out on his travels, sent Bhai Mardana to procure a rabab, i.e. rebeck. Bhai Buba and his father, Bhai Amir Bakhsh Rababi, were widely respected among Sikhs as much for their honoured lineage as for their status in the rababi school of Sikh music.

Association with them encouraged Gajja Singh to master, besides classical music, the traditional Sikh kirtan. After finishing studies with Mir Rahmat Ali, Bhai Buba went to Bahawalpur state as chief court musician, and Bhai Gajja Singh returned to Gurusar where, after the death of his patron, he succeeded him as mahant. An akhara or seat of the Nirmala sect, to which the mahants of Gurusar belonged, had been established at Patiala in 1861.

Mahant Gajja Singh visited there regularly, especially during the rainy season, and his performance both as a vocalist and instrumentalist attracted wide notice. His virtuosity in playing on the taus, a bow instrument with frets like a sitar, had become proverbial. He had a style of his own and, copying his master Mir Rahmat Ali's vina, sur-bahar and sitar, he was able to produce the effect of jhala or jhankar, i.e. trilling, on his taus. Bhai Kahn Singh of Nabha, scholar and encyclopaedist, who had attended some of his performances, wrote in his Gurushabad Ratnakar Mahan Kosh:

"Bhai Gajja Singh has been a peerless pandit of music. Those who have listened to his alap or melody on the taus can never forget him."

Mahant Gajja Singh continued to enjoy the patronage of ruling princes of Patiala. Maharaja Bhupinder Singh (1891-1938) in fact served a period of apprenticeship with him learning classical music. At the Delhi Darbar of 1911, Gajja Singh gave a memorable performance representing the Patiala Gharana of music. He was rewarded with the grant of a free railway pass for life to travel anywhere in India for the propagation of his art. Encouraged by Maharaja Bhupinder Singh, he took up the project of recording the original rits, i.e. forms or modes of the ragas as set by Guru Arjan and preserved orally by Sikh musicians.

The work had been undertaken during the time of Maharaja Ranjit Singh by the Nirmala Mahant of Dera Baba Mishra Singh in Amritsar, but it had remained incomplete. However, the then priest of Dera Baba Mishra Singh, Mahant Kapur Singh, was invited to Patiala. Two other helpers appointed were Mahant Mela Singh and Baba Dial Singh Kairon. Already in 1910, Bhai Buba had, at Mahant Gajja Singh's persuasion, joined the Patiala court. Ram Krishan Singh, a junior mahant at the historical Gurdwara Motibagh, was co-opted as adviser on Sanskrit musical terminology, and Bhai Durga Singh, the best-known calligraphist of Patiala at the time, was engaged as the scribe. Mahant Gajja Singh, as the head of the team, started work on the thirty-one ragas of the Guru Granth Sahib, with an introductory part covering two of the three initial compositions, Rahras and Kirtan Sohila, which form part of the daily devotions of the Sikhs. He had also taken up the five chaukis, i.e. daily choruses or hymn-singing sessions, and some of the Vars in different musical measures when death intervened. Mahant Gajja Singh died on 12 June 1914, and the work was left unfinished.

Source: Encyclopaedia of Sikhism, Harbans Singh