Origins and use
The instrument comes in three chief varieties: a long wooden plank held in the player's left hand and struck with a wooden mallet in the right; a larger, heavier, fixed timber block suspended by chains and struck by one or two mallets; and a fixed metal variety, often horseshoe-shaped and struck by a metal mallet.
The portable semantron is made of a long, well-planed piece of timber, usually heart of maple (but also beech), from 12 feet (3.7 m) and upwards in length, by 1 1⁄2 feet (46 cm) broad, and 9 inches (23 cm) in thickness. Of Levantine and Egyptian origin, its use flourished in Greece and on Mount Athos before spreading among Eastern Orthodox in what are now Bulgaria, Romania, Moldova, Serbia, Montenegro, Bosnia and Herzegovina and the Republic of Macedonia. It both predates and substitutes for bells (first introduced to the East in 865 by the Venetians, who gave a dozen to Michael III), being used to call worshipers to prayer. The metal variety is made of iron or brass (ἁγιοσίδηρα, hagiosidera / клепало, klepalo); formed of slightly curved metal plates, these give out a sound not unlike that of a gong.
In the portable wooden form, at the centre of the instrument's length, each edge is slightly scooped out to allow the player to grasp it by the left hand, while he or she holds a small wooden (or sometimes iron) mallet in the right, with which to strike it in various parts and at various angles, eliciting loud, somewhat musical sounds (κροῦσμα, krousma). Although simple, the instrument nonetheless produces a strong resonance and a variety of different intonations, depending on the thickness of the place struck and the intensity of the force used, so that quite subtle results can be obtained. A metal semantron, smaller than those of wood, is usually hung near the entrance of the catholicon (the monastery's main church). In the traditional monastic ritual, before each service the assigned player takes a wooden semantron and, standing before the west end of the catholicon, strikes on it three hard and distinct blows with the mallet. He then proceeds round the outside of the church, turning to the four quarters and playing on the instrument by striking blows of varying force on different parts of the wood at uneven intervals, always winding up the "tune" with three blows similar to those at the beginning. Where there is a metal semantron, it is customary to strike it after the wooden one has been played. The semantron is sounded every midnight for night offices (Midnight Office and Matins); this is done by the candle-lighter (κανδηλάπτης, kandilaptis). The semantra are usually suspended by chains from a peg in the proaulion (porch of the catholicon) or perhaps outside the refectory door, or on a tree in the courtyard.