TIME-SIGNATURE (Lat. Signum Modi, vel Temporis, vel Prolationis; Germ. Taktzeichen). A Sign placed after the Clef and the Sharps or Flats which determine the Signature of the Key, in order to give notice of the Rhythm in which a Composition is written.
Our present Time-signatures are directly descended from forms invented in the Middle Ages. Mediæval Composers used the Circle—the most perfect of figures—to denote Perfect (or, as we should now say, Triple) Rhythm; and the Semicircle for Imperfect or...