Croon

Schmachtfetzen

(soft, low-pitched sound; soft or sentimental hum, song, or tune)

Schnulze

(soft, low-pitched sound; soft or sentimental hum, song, or tune)

gefühlsbetontes Lied

(soft, low-pitched sound; soft or sentimental hum, song, or tune)

sentimentaler Schlager

(soft, low-pitched sound; soft or sentimental hum, song, or tune)

summen

((transitive, intransitive) to hum or sing (a song or tune) softly in a low pitch or in a sentimental manner; to sing (a popular song) in a low, mellow voice)

säuseln

((transitive, intransitive) to hum or sing (a song or tune) softly in a low pitch or in a sentimental manner; to sing (a popular song) in a low, mellow voice)