I explore some similarities between experiences of music and of analytic sessions. I focus on qualities of evanescence, the way that music – in contrast to many other arts – in one perspective only lasts as long as it is actually being played. Then it’s over. The analyst-patient discussion in a session is similar. Yet the psychic reverberations of some transient, fugitive moments may last a lifetime. And even when no verbally profound understanding is occurring, nevertheless the patient-analyst encounter is emotionally significant. I illustrate this with a clinical example. I explore transference as illusion, and the relationship between truth and illusion in terms of Bion’s O. I end with thoughts about the paradoxical value of the illusoriness of aesthetics and nature as considered by Freud in his short paper “On Transience” (1916), and the grin of Lewis Carol’s Cheshire Cat, left hanging in the air.