Folio 34 of manuscript Ms Lynar B3 contains two compositions. Where the first (published two days ago) is a full fledged composition, the second is more a sketch. It could be meant as a model for improvisation of as a model for composition. Or perhaps it is no more than what is written: a few bars of music to establish a mode or a tonality. It certainly can be used as such. If you need something to fill up some time, and that's not longer than a minute or so, well, here it is.
Score available here: http://partitura.org/index.php/anonymus-praeludium-pedaliter