In diatonic set theory, Rothenberg propriety is an important concept, lack of contradiction and ambiguity, in the general theory of musical scales which was introduced by in a seminal series of papers in 1978. The concept was independently discovered in a more restricted context by , who termed it coherence. For example, the major pentatonic scale is strictly proper: The pentatonic scales which are proper, but not strictly, are: The one strictly proper pentatonic scale: * {0,2,4,7,9} (major pentatonic) The heptatonic scales which are proper, but not strictly, are: