In many of Vermeer's works, there is a feeling of serenity and quiet, and in others, such as this one, there is an indication of action without disturbing the essential stillness. Here, the momentary movement is derived from an interruption, as a man enfolds the girl. He is ambiguous, either teacher or lover, trying to draw her attention to a letter, yet she is looking at us, not him, her expression quizzical. In the foreground is a chair with a comfortable cushion, and we may decide to sit on the chair or not.
While love is symbolized by music, on the wall is a painting of Cupid holding a bow and a card, based on one by Cesar van Everdingen. This picture can also be seen in A Lady Standing at the Virginals. The bow is for shooting the arrows of love, the card to indicate that love is a matter of chance.
On the table, with the musical instrument (a cittern), is a pitcher and a glass of wine; perhaps he has been drinking the wine, or perhaps he is trying to dissuade her from music so that she can drink with him. The wine on the table does not bode well for the relationship: see The Officer and Laughing Girl, The Glass of Wine, and The Girl with the Wineglass for other pictures of women being seduced with the help of demon drink. This particular combination of music teacher, lover, and a pitcher of wine, is also evident in The Music Lesson.
The birdcage on the wall is a symbol of how the girl should be behaving; but it was added later by another painter.