When there are 5 beats to a measure, with prin. accents on 1st, and 3rd or 4th beats according to whether the 5 are a compound of 2/4 and 3/4 or of 3/4 and 2/4. Famous examples are in Chopin's pf. sonata in C minor, Op.4, Wagner's Tristan und Isolde, Act III, Sc. 2, and Tchaikovsky's 6th Sym. (2nd movt.).