Musical set theory provides concepts for categorizing musical objects and describing their relationships. Many of the notions were first elaborated by Howard  in connection with tonal music, and then mostly developed in connection with atonal music by theorists such as Allen , drawing on the work in twelve-tone theory of Milton Babbitt. The concepts of set theory are very general and can be applied to tonal and atonal styles in any equally tempered tuning system, and to some extent more generally than that.