What a day to ask these questions...I'm avoiding barbecued meats in order to write this.
I was hoping some people could clarify some questions that I had:
1) At various points in the liturgy, the text indicates that there will be a Husoyo prayer which seems to be composed of a Proemion and a Sedro and sometimes a Qolo, Etro, Eqbo and Huthomo. What do all these words mean and what are their functions? I think I have a general idea but sometimes each of these words never appear alone and have to appear with the others, like a Proemion and a Sedro, while others can appear alone in the text without any of the others, like an Etro or a Huthomo. Also, are they silent prayers or loud prayers?
First, some terms.
Proemion: a "preface" to the Sedro
Husoyo: prayer of "absolution" (forgiveness)
Sedro: a longer prayer, usually organised or "ordered" (hence the name) according to one or more themes
There is always a proemion attached to a sedro. In the Liturgy of the Catechumens of the Holy Qurbono, and at Vespers and Matins before a Qurbono, the husoyo is read in between. But these are not the only places where the proemion/sedro unit appear--they also appear in the orders of festal services, the canonical hours, the orders of sacraments, etc. During these prayers, incense is offered by the priest. Only a priest or a bishop can say the proemion and husoyo, while the sedro can, at times, be delegated to a deacon with the blessing of the presider.
Etro: prayer of incense
Usually, but not always, services may have a separate prayer for the offering of incense. This prayer, called "etro" ("fragrance") is also read by the priest, who offers the incense as well.
Qolo: a "hymn"
Eqbo: a type of hymn which begins or ends ("termination") a series of qole, and is thematically linked to them (while not a perfect analogy, the eqbo functions like the irmos in a Byzantine canon)
Huthomo: a concluding prayer or hymn which "seals" the prayer
Generally, these units appear in a certain order. I will use the pattern of the daily Vespers as an example:
Quqlion (select psalm verses sung to one of the eight tones)
Bo'outho (a hymn of "supplication"; it has by and large replaced Litanies, which now appear only in the Liturgy and in some other sacramental/festal rites)
Depending on the type of service or rite, some of these elements may not always be present, but this is the basic order, and they wouldn't appear in a different order. It's a fairly stable structure upon which all our services are built.
Also, these prayers are generally said aloud.
2) During the video, however, they don't always talk about or show the praying of these Husoyo Prayers where the text indicates. They only show and talk about the Husoyo prayers that happen after the readings. What's going on here? I know sometimes in other liturgies that a litany or a hymn will be chanted by the deacon and congregation while the priest is performing rites and saying special quiet or silent prayers at the altar so am I supposed to think that the Husoyo prayer is being prayed by the congregation and the deacons outside of the veiled sanctuary while the priest is inside the veiled sanctuary doing the prothesis/preparation of the gifts, vesting, etc.?
Strictly speaking, the husoyo prayer is used once in the Liturgy and once each at Vespers and Matins on the day the Liturgy is served. But in the Middle East, sometimes the whole unit (proemion-husoyo-sedro) is called "husoyo" as a sort of shorthand. In India, "husoyo" is not the shorthand for this unit...people use either "proemion" or "sedro".
That series of videos shows, among other things, the preparation of the gifts and the vesting of the priest. These rites are usually performed by the priest during the singing of Matins; the singing you hear over the priest's silent prayers is Matins.
3) The text says that the priest chants the beginning of the Husoyo but who says the rest of these prayers, the proemion, the sedro, etc.? Is it the priest or the deacon?
In the Liturgy of the Catechumens, the celebrating priest typically says all of these prayers. The only exception is when a priest celebrates in the presence of a bishop: the bishop will read the proemion and husoyo, and the priest will read the sedro. But he could also just let the priest do them all.
4) If you look at the left-hand side of the page and click "Supplications", you get to a page filled with Husoyo prayers. When are these supposed to be said? In between the Kiss of Peace and the Anaphora? Are they just replacements of the Husoyo prayers under "Public Celebration" and it depends on the feast or on the liturgical calendar?
They are "replacements" for what you find under "Public Celebration". A proemion is always matched to its own sedro, but there are a number of these specifically for use in the Liturgy. You can pick any one set out of these, but you can't mix and match (e.g., you can't pick Proemion 2 and Sedro 9). Some of the choices on that page have descriptions "for weekdays" or "for feasts of the Lord", but that's more of a suggestion than an actual rubric--the Indian books make no such distinctions, and I'd be surprised if the Syriac books had those distinctions early on and it never saw the light of day in India.
5) Can anyone point me to more resources, on-line or off-line, that can shed some light on the origins and history of these prayers? Preferably something in-depth and scholarly that talks about the primary resources and manuscripts in which we can detect the forerunners of these prayers or when they first appeared.
That's the best basic introduction available in English; the bibliography will be useful for further research. Also, Robert Taft's book on the Liturgy of the Hours has a good section on the West Syriac divine office and the meaning of a lot of these terms, but he unfortunately uses Eastern Catholic liturgical books rather than Orthodox books as his primary source, and that leads to inclusions and exclusions that are foreign to Orthodox practice being labelled as "Syriac tradition". Gregory Woolfenden's book on the Liturgy of the Hours is, IIRC, better than Taft in this regard. Both are useful.