A ragi performs kirtan, the devotional singing of hymns, shabads, from the Guru Granth Sahib set to specific classical ragas, musical modes, many of which the scripture itself explicitly specifies for particular hymns, reflecting founder Guru Nanak's own practice of composing and singing his teachings accompanied by music from the beginning of the Sikh tradition; Guru Nanak's longtime companion and musician, Bhai Mardana, a Muslim who traveled with him for decades playing the rebab, is traditionally regarded as the first ragi in Sikh history, establishing music as integral to Sikh devotional practice from its very founding rather than as a later addition.
A ragi typically performs as part of a small ensemble accompanying themselves on instruments including the harmonium and tabla, and formal training in the specific classical ragas associated with Sikh kirtan, as opposed to devotional singing more generally, is provided through dedicated institutions and, traditionally, through apprenticeship under an established ragi; kirtan holds a place in Sikh worship the tradition treats as considerably more central than accompaniment to prayer, understood instead as a direct spiritual practice and vehicle for connecting with the divine in its own right.