An octatonic scale is any eight-note musical scale. The scale most often meant by this term is one in which the notes ascend in alternating intervals of a whole step and a half step, creating a symmetric scale. In classical theory, in contradistinction to jazz theory, this scale is commonly simply called the octatonic scale (or octatonic collection), although there are forty-two other non-enharmonically equivalent, non-transpositionally equivalent eight-tone sets possible.
In St. Petersburg at the turn of the 20th century, this scale had become so familiar in the circle of composers around Nikolai Rimsky-Korsakov that it was referred to there as the Korsakovian scale (Корсаковская гамма) (Taruskin 1985, 132). As early as 1911 the Russian theorist Boleslav Yavorsky described this collection of pitches as the diminished mode (уменьшённый лад), because of the stable way the diminished fifth functions in it (Taruskin 1985, 111–13, citing Yavorsky 1911), and in jazz theory it is called the diminished scale (Campbell 2001, 126), or symmetric diminished scale (Hatfield 2005, 125), because it can be conceived as a combination of two interlocking diminished seventh chords, just as the augmented scale can be conceived as a combination of two interlocking augmented triads. In more recent Russian theory the term "octatonic" is not used. Instead this scale is placed among other symmetrical modes (total 11) under its historical name Rimsky-Korsakov scale, or Rimsky-Korsakov mode (Kholopov 1982, 30; Kholopov 2003, 227). Because it was associated in the early 20th century with the Dutch composer Willem Pijper, in the Netherlands it is called the Pijper scale (Taruskin 1985, 73).