Belgium: Composers

This booklet strip of 5 stamps (Scott #2131) was issued by Belgium 1/23/2006. It features several early composers, on the stamps themselves, and in the selvage. The composers include Josquin de Prez, Guillaume Dufay and Gilles Binchoise (who is holding what looks like a lyre of some type), Johannes Ockeghem (with men gathered around a music desk), Jacob Obreacht, Adriaan Willaert and Orlandus Lassus. And then, most interestingly, in the left-hand selvage is a little positiv organ. It appears that it is actually the left-hand side of the image that includes Dufay and Binchois, but the stamp perforations create a gap. It's difficult to tell how large this instrument is and whether it might actually be movable, and thus a portativ.