Sat Nam, Yves Ji -
First and foremost, Gurbani comes from the heart.
Today there is a lot of preoccupation with classical raag performance (Gurbani Sangeet) to the extent that often the focus on the technical aspect of the performance of Raag and taal detracts from the poignancy of the the Guru's words. Such ragis appear to forget that the spirit of Gurbani is expressed in gentle, melodious and soulful music that opens the heart with its essence and its fragrance.
The aim of kirtan is to uplift us and awaken the longing of bhakti and the bliss of sahaj. This happens when the singer forgets the music and becomes the music. When the ragi is an open channel through which the melody and rhythm exist in the moment in a continuous, calm, harmonious and melodious flow.
Guru Nanak spoke of the pleasure of Shabd as the "ras" (juice, essence, nectar) and of being penetrated and saturated with the feeling of the music in the way that crimson dye spreads through a white cloth penetrating every fiber, every molecule of the cotton.
So, by all means sing in raag if you understand how to do that. After all, the system of ragas is designed to evoke a specific feelings in the musician and the listener through the phenomenon of resonance. But never forget that the purpose of Gurbani is to "fly under the radar" of the rational mind and land squarely in the heart.
When I listen to Ragi Harjinder Singh Ji, Nirinjan Kaur (Oregon,) Snatam Kaur, Australian World Music singer Dya Singh, Jagjit Singh and Ustad Rashid Khan, the sound of their voices opens my heart and makes me feel within myself the longing to merge with the One that is the very core and essence of Gurbani.