I thought it rather interesting that five-line staffs were used, instead of the four-line staff we've come to associate with chant. Does anyone know if this was common in the 16th Century?

The martyrs-hymn that Prof. Mahrt's choir sang at the Colloquium Vespers was notated on a five-line staff, so I suppose this wasn't an unknown practice.

The link posted leads us directly to the first line of responsory «Collegerunt pontifices», p. 143 in the 1908 Graduale Romanum, from the bessing of Palms on Palm Sunday. This one is no hymn! German neums are used. There are (as expectable) some differences in the melody to the one in the GR, but the piece is perfectly recognisable.

Isn't there a way of accessing items such as this other than these irritating and bothersome endless series of letters and symbols?
Most of these irksome codes I usually ignore, but this one proved worth the effort.

This responsory is a truly interesting specimen. As for the five line staff: it appeared earlier than most people think. I have seen (and I'm sure many colleagues here have, as well) examples as early as the XV. century and, I seem to recall, even a few from the late XIV. century.

(Incidentally, while speaking of staves, remember to say a prayer for Guido - he said that people would be so grateful for 'his invention' that they would pray for his soul because what formerly took them ten years to learn they could now learn in two.)

So that it turns out like this:

See this book of processional hymns

Forgive me if that wasn't what you were asking.
(Save the Liturgy, Save the World)