Rudolf Fischer writes from Budapest, following up his remarks in A late comment, by Rudolf Fischer, Saturday, July 10. 2010;
How frustrating, dear James. True, I have found ISON in Wikipedia but not as an independent article. Ii is mentioned e.g. in an interesting short article on the STAVROPOLEOS CHURCH or MONASTERY in Bucharest. At a crucial point the English appears a bit fractured but reference to MANASTIREA STAVROPOLEOS in the Rumanian Wikipedia, from which the English is quite obviously translated, should clear up any ambiguity.
By the way, have you looked up the NEW GROVE DICTIONARY OF MUSIC which I presume is available in your Carnegie Library.
I shall write to my koumbaros Dimitri Gallanis, retired headmaster of a Secondary School. Both he and his wife, who taught Ancient Greek, are accomplished church musicians.
What really matters is, of course, not terminology, but das DING AN SICH. Forgive but I simply don't know how to give you links which you can click, and I will refrain from explaining to you how you can get Mount Athos monks chanting psalms, canticles &c on YOUTUBE. I refuse to teach my grandmother how to suck eggs.
When you listen you should also, in every case, whether the melody is carried by just a single psaltis, or by a small choir, hear an accompaniment, a sustained note which to an untrained ear sounds like a very pleasant and moving drone. Well. that is the ison.
Ed: Thanks, Rudi, So an ISON is a single, sustained note played as an accompaniment in church music?