To sing softly or in a low voice, especially in a sentimental manner.

To speak or sing in a gentle or whispering manner.

धीरे-धीरे बोलना या गाना

English Usage: He was crooning sweet nothings into her ear.

Hindi Usage: वह उसके कान में धीरे-धीरे प्यार भरी बातें कर रहा था।