NEW DELHI—Prime Minister Narendra Modi spent the first half of 2023 working on a secret project: a song about millet.

The pop-rock tune—performed by a Grammy Award winning singer with a section featuring Modi speaking about the prosperity and radiance of millet—extols the virtues of an ancient grain that has been cultivated in Asia and Africa for thousands of years. Modi’s government declared 2023 the Year of Millets, saying the grain could help alleviate world hunger, boost health and help small farmers.