The article explores and analyses the musical development of an infant from birth to the beginning of her third year of life. Detailed analysis addresses the months 20–25. The object of analysis is Marie, daughter of the first author, whose development has been recorded by her parents in the form of diary entries as well as video and sound recordings used in the analysis. Marie began to speak at 19 months and to sing at 20 months. The development of singing skills is illustrated by an analysis of her presentations of children’s song („The big old deer”) and two improvised songs. In Marie’s case acquisition of speech was a prerequisite of singing. At first, recognizable elements of lyrics began to emerge, then the melody. The child could hum the melody of a children’s song only after she had learnt it together with the lyrics. Her abilities to sing children’s repertoire and to vocally improvise developed parallelly. At first, her musical self-expression evolved on an individual level (as vocalised inner speech), while at 23 months there was added appreciation of singing as a social activity, an ability and wish to sing along with others, and to initiate such activity.