In Joseph Herl’s excellent Worship Wars in Early Lutheranism: Choir, Congregation, and Three Centuries of Conflict, he quotes Luther responding to his congregation in Wittenburg after the introduction of the German Mass. He is, to say the least, a bit underwhelmed at their singing. “On January 24, 1529, Luther chastised the people again over their failure to sing what they had been taught,” says Herl.
I see your idleness, how you fail to learn those sacred songs sung every day and how for nearly two years now you have had no interest whatsoever in those enduring songs of the schoolboys, but rather pay much more attention to popular ditties. Would that you fathers might strive to train those under your care! For such songs are a sort of Bible for the uncultivated, and even for the learned. See how the pious are set on fire through these songs! Observe the efficacy and power of Ein Kindelein so lobelich! That child has preserved the church: “Had this little child not been born for us, we would surely all have been lost”; likewise with Nun bitten wir den Heiligen Geist. And so we took care that a large number of the best spiritual songs might be composed for your use and edification. Therefore work hard that you might learn and cultivate them with greater diligence than you have up until now.
Eventually they did adopt his music warmly. About 100 years later, Hieronymous Praetorius was still using one of those tunes he mentioned, “Ein Kindelein so lobelich.”