Ison is the name given to the fundamental tone of a hymn or psalm chant, which is placed beneath it like a drone as a held tone. In Byzantine choral notation this word also denotes the neume for tone repetition. Ison means “the same”.

In larger hymns the Ison follows the tetrachords; that is, as soon as the melody moves into the upper tetrachord, one sings the fundamental tone of that tetrachord. Further changes of Ison are also possible as musical expression and are used in practice. Nevertheless the character and symbolism of the Ison remain the same: it always forms a lasting harmonic basis for the melisma that moves above and around it. Therefore in classical chant the Ison must not be changed frequently, and certainly not continuously. Even dissonant intervals by no means force a change of Ison. On the contrary, the character of the mode becomes recognisable precisely through the sharpness of certain intervals in relation to the Ison.

In its harmonic numerical value the Ison corresponds to the 1; it is thus an image of the beginning, of the origin, and therefore a symbol of the eternal primal ground, God himself. Since the Ison contains all possibilities within itself, yet still stands before unfolding into musical melos, it is a symbol of the virginal primal ground of being on the eve of creation: “The Spirit of God hovered over the waters”, as the book of Genesis says. Thus the Ison is more particularly a symbol of God the Father, the Creator, the unknowable and unspeakable primal ground. In what resonates perceptibly within it, it is a symbol of the third form of the Godhead, the Holy Spirit. Also in Christian numerical symbolism the 1 implicitly states the 3, and with the 1 necessarily the 3, for the Holy Trinity of Father, Son and Spirit is the one God in three forms (hypostases), undivided and unconfused.

A Serbian elder of modern times once expressed these connections during a spiritual synaxis in an Athonite monastery with the words: “the Ison in Byzantine church music is the proof of the apophatic theology of the Orthodox Church”.

As soon as the melisma rises out of the Ison, the second form of the divine Trinity enters the symbol: the Logos, the Eternal Word. At the beginning of the Gospel of John it says: “In the beginning was the Word, and the Word was with God, and the Word was God. All things were made through him, and without him was not anything made that was made. In him was life, and the life was the light of men.” As soon as the Word comes over “the waters of the beginning”, all things enter into being. The Word has creative almightiness. “God created all things through his Word.” The Word is also God in his incarnation, the eternal Logos who brings life. The melos of chant grows on all levels out of the word, down to the natural accent and syntax of language. Yet it is not exhausted in its outward form; rather, it is an analogous bearer of the archetypal dimension of the holy text. This dimension is indeed already contained in the text itself and opens itself to the praying reader in the Holy Spirit. But in the melos there lies at the same time a second, more immediate way of its “incarnation”. Ideally, the choral melos is the “echo of the Word before all words”, of the thoughts of God, which in spiritual vision present themselves as archetypes of beings and possibilities of becoming.

The harmony of choral melos consists, before all music-theoretical considerations, in the consonance of spiritual energies and powers with divine thoughts and archetypes. Thus the relation of the melos to the Ison depicts the eternal binding back (religio) of formed being to the primal ground of all being.

In this interplay of Ison and melos, the third is also revealed, which nevertheless is already contained in the one as in the other. Jesus says in the Gospel of John: “I and the Father are one” and “Whoever has seen me has seen the Father.” But this “seeing” is awakened in the Holy Spirit. When Simon Peter says to Jesus: “You are the Christ, the Son of the living God”, the Lord answers: “Blessed are you, Simon Peter, for flesh and blood has not revealed this to you, but my Father in heaven.” The Spirit is not named directly there, but it is he who awakens every spiritual knowledge; he acts through his indwelling in man and communicates divine grace and power. Only at Pentecost could the apostles speak in the “primordial language”, and that means at the same time: in all languages of the world. As the Spirit of God hovers over the waters of the primal beginning, as the Spirit of God lets the Eternal Word and the Father be known, so he moves the holy play of love among the powers. He is the all-present and all-fulfilling, loving, eternal God. In essence (kat ousian) he is one with the Father and the Son; in hypostasis (kat ypostasin) he is unique and independent, just as the Father in himself and the Son in himself. Thus the Holy Trinity is unconfused and undivided, the one God in three forms.

In the recitation of the holy texts the Ison appears purely. Every liturgical recitation takes place on an ever-same tone, the symbol of the eternal primal ground, and thus shows the recited text to be holy, the word of the Father, the Spirit-wrought word of the eternal Church.

When the Ison is sung in the services, this has not only a musical meaning. The monk, just like the lay church singer, learns to join the Ison with spiritual prayer. There is a mysterious inner relationship between the practice of spiritual prayer and the Ison. It is not simply given automatically through the musical practice of the Ison, although the Ison contains precisely this spiritual potency; it always also depends on the consciousness and right inner attitude, on the spiritual orientation and proper tension of the singer. The Ison as a merely outward, “fleshly” sung acoustic phenomenon still lacks spiritual illumination. Whether the symbol becomes effective depends on the singer and on the Holy Spirit and on their cooperation.

This applies to sacred chant as a whole, just as to all other disciplines of theourgy. The singer, the acolyte, the deacon, the priest, every monk present: all must grasp the spiritual meaning and carry it through in the melos as in the holy action, so that through the words the Eternal Word may shine through. Then Spirit-filled chant draws away the veil of outward understanding and opens heart and mind to the vision of meaning and archetypes.