Spanish Chant

I have just come back from Andalucia, choosing to flee the country and spend the Easter Octave away from Wedding-mania.

One of the places we visited was Ronda and I was struck by something I saw concerning it’s music…

No not this kind of music. This kind of music:

This picture was taken in Santa Maria la Major in Ronda. Here is the Lauda Sion, the sequence for Corpus Christi but it looks rather different. Firstly, it is written on a five-line stave. Secondly, it is not the usual chant melody.

And there were more manuscripts on display, all with five line staves.

Does anyone know where this originates from?  As far as I know Mozarabic Chant if it was written down was always on a four line stave.