There are songs of Thakura Narottama Dasa, one of the acaryas in the Gaudiya-sampradaya, composed in simple Bengali language. But Thakura Visvanatha Cakravarti, another very learned acarya of the same sampradaya, has approved the songs by Thakura Narottama Dasa to be as good as Vedic mantras.
– from Srimad Bhagavatam 1.10.20
…. also ….
The prayers of Narottama Dasa Thakura, this sound is above the material platform. It is directly from the spiritual platform. And there is no need of understanding the language.
It is just like a thunderburst. Everyone can hear the sound of thunder–there is no misunderstanding. Similarly, these songs are above the material platform, and they crack like thunder within your heart. There is so much depth of meaning in Narottama dasa Thakura’s prayers.
– Srila Prabhupada