Akathist - a hymn dedicated to a saint, holy event, or one of the persons of the Holy Trinity. The word akathist itself means "not sitting."
Antiphon - consists of one or more psalm verses, alternating with verses that contain the fundamental thought of the psalm. The name derives from the traditional practice of their being sung by two choirs, each responding antiphonally to the other.
Aposticha - are a set of hymns (stichera) and verses towards the end of Vespers and Matins. The Greek literally means "hymns on the verses (stichos)."
Kontakion - is a type of thematic hymn in the Orthodox Church. Originally, the kontakion was an extended homily in verse consisting of one or two proemia (preliminary stanzas) followed by several strophes called oikoi (also ikoi; singular oikos, ikos), usually between 18 and 24.
Prokeimenon - is a liturgical verse or scriptural passage sung or read before the apostolic reading.
Sticheron - (stichera - plural) is a type of hymn used mainly in Vespers and Matins. A sticherarion is a book containing the stichera for the morning and evening services throughout the year.
Troparion - (troparia - plural) is a type of hymn in the Orthodox Church. It is a short hymn of one stanza, or one of a series of stanzas; this may carry the further connotation of a hymn interpolated between psalm verses.
An acoustical engineer at Stanford recreates the acoustics in Hagia Sophia with the singing of the Cappella Romana. The 8-11 second reverberations of the singing recreated thusly gives an extraordinary effect to the recording, giving us an idea of why the combination of the visible rich decoration, the smell of incense, this music, and the deep spirituality of the moment would have such an extraordinary effect on those in attendance. (An insight roughly cribbed from the presentation of Dr Bissera Pentcheva at the Huffington Ecumenical Institute's Icons and Images Symposium in February, 2013 -- T. A.)
Znamenny chant (click to listen) was the principal chant of the Russian Orthodox Church from the time Christianity was imported from Byzantium to roughly the late seventeenth century. The illustration above is znamenny notation with Shaidurov's red (cinnabar) letters designating the height and inflection of tone. The excerpt is an Irmos, the theme-song of each of nine canticles introducing the tropar and the hymn of the Feast. It is taken from the book Irmosy tserkovanago znamenny penia, and published by the Knigoizdatelstvo Znamenny Peniye, Kiev, 1913. (Nicholas Brill, History of Russian Church Music, Bloomington, IL: Nicholas Brill, 1980)