A fundamental question in the perception of melody is how listeners use pitch information to arrive at a sense of musical scale. We investigated possible ways in which this might be achieved. Listeners were required to detect notes incompatible with scalar structure in the course of melodic sequences. Within the parameters of our experimental sequences, the results showed that detection of nonscalar notes could be based on identifying nonscalar interval combinations (e.g., F♯, A, Bb), as well as by matching successive notes to a developing scalar schema. The strength of the scalar schema was influenced by relations between notes in the circle of fifths, with notes closer together in the circle of fifths (e.g., C, G, D, A) leading to a stronger schema than notes further apart (e.g., C, G, E, B).