Lampadarios, a term derived from the Latin lampada (candle) - also lampas, in some Orthodox Christian traditions during recent centuries refers to the leader of a second (left) choir of singers, although its original meaning applied to torch carriers.
Originally, the term, lampadarius (plural lampadarii), applied in ancient Roman times to slaves who carried torches in procession before consuls, emperors, and other officials of high dignity during the latter days of the Roman Republic and then under the Empire.
While there has been no special reason to attribute to the lampadarii any Christian ecclesiastical character, their function was imitated by acolytes and other clergy, carrying torches/lanterns/candles in their hands, who preceded a bishop or celebrant in solemn processions including those to the altar.
The term "lampadarios", since the end of the Eastern Roman empire, has been used as a title of a lower order of clergy as well as designating the leader (cantor) of a second choir of singers in some Orthodox Church practices. He is usually a candidate for promotion to Protopsaltes (First Cantor) and Archcantor. The lampadarios is also entitled to act as a witness at various important acts of the Church. 
- "The Cantor in the liturgical life of the Church", official site of the Apostolic Deaconing of the Church of Greece (in Greek language)