High Quality Content by WIKIPEDIA articles! Sub Arturo plebs – Fons citharizantium – In omnem terram is an isorhythmic motet of the second part of the 14th century, written by an English composer known by the name of Johannes Alanus or John Aleyn. It stands in the tradition of the Ars nova, the fourteenth-century school of polyphonic music based in France. It is notable for the historical information it provides about contemporary music life in England, and for its spectacularly sophisticated use of complex rhythmic devices, which mark it as a prime example of the stylistic outgrowth of the Ars nova known today as Ars subtilior. It has been dated conjecturally to either around 1358, which, within that school of composition, would make its compositional technique exceptionally innovative for its own time, or some time later during the 1370s.