This article illustrates some ways in which observations of typically-developing infants can inform music therapy and other work with children with disabilities. The research project that is described examines typical infant development with special attention to musical relatedness and communication. Videotapes of sessions centering on musical play with typically-developing infants and of music therapy sessions of children with multiple severe disabilities are examined in light of developmental issues, conceptual frameworks, and relationships between typical development and developmental issues of children with disabilities. Greenspan's model of psychosocial development is used as a basis for analyzing observations.