This booklet strip of 5 stamps was issued by Belgium. 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.