Jambe de Fer

A little quote I happened to stumble while doing research for my thesis:

What difference is there between Music & Singing, between musician and singer? There is as much difference between a poet and the reader of poetry: for the poet is inventor and maker of the thing, without which the reader could read nothing. Likewise the Musician is inventor & composer of some Music, without which the singer could not show off (or make heard) his voice.

Philippe Jambe de Fer, Epitome Musical (Lyons, 1556)

So tell me, were singers back then not musicians? Are singers now not musicians?