It doesn’t matter whether one is accompanying the kirtana with karatalas,
mrdangas, and harmonium; using a drum set, electric keyboard, and bass
guitar; decorating the kirtana with flute and violin; or even just clapping
one’s hands. One can chant with very melodious classical ragas, or one can
sing raucous, hellacious, heavy metal chanting, to attract certain people.
One can sing ten tunes an hour or one tune every ten hours, sing in complex
rhythmic patterns or a simple rhythmic one. One can have jumping, dancing
kirtana or very slow, contemplative kirtana. No matter what you do, no
matter how you decorate the kirtana, if such chanting is not done with pure
devotion, it will never ever inculcate bhakti into the heart of anyone.