Valerie,

Our local specialists hereabouts will chime in when they see your question, but for now let me observe that "Sarum" refers to a rite in use in England since before the Protestant revolution of the 1530s. I don't believe it is still widely used, but I think its discontinuation had little or nothing to do with the late Council.

I know the Harris piece well. I own a copy (somewhere). When you say you want to know how to categorize it, what sorts of details do you want?

Valerie: to enlarge on what CGZ wrote.
Sarum is an older name for the city (and diocese) of Salisbury in Southern England.
'Sarum Antiphon' just means a piece of chant that can be traced to the liturgical books of Salisbury.
In the Middle Ages most Catholic dioceses had variants in the way they celebrated the liturgy, and in the tunes and texts. For some reason the books used in Salisbury gained a dominant position in liturgy in England, and before the Reformation that was reinforced by kings wanting a degree of uniformity of practice. So 'Sarum' tends to be used as shorthand for 'Coming from English pre-Reformation Catholic practice'
[Afterthought]In the 19th century liturgically minded Anglicans translated much of this into English, so 'Sarum' also refers to pre-Reformation liturgy translated.