The notion of the signature could serve as an appropriate metaphor by which to explore Heinrich Isaac as a man of his time and world. It may be mere coincidence that he has left more documents signed in his own hand than contemporary composers, but some of the documents he authenticated in this way really do attest to a new idea of professional musicianship that Isaac was the earliest and most successful in implementing: that of the professional composer who undertakes to produce new works under contractual obligation. Isaac is the first-known musician who signed a document specifically in this capacity. Yet his signature, or at least the assurance that he personally composed and signed a musical work, is also found in the context of practical musical sources, where they would appear to have no legal significance. Martin Just has shown, however, that the particular folios containing these compositions, in the manuscript Berlin 40021, were originally sent as letters. The implication is that Isaac's signature, in this case, is not an attribution so much as a mark of authentication—something that would have been required only if the musical works in question were sent, and changed hands, as part of a commercial transaction.
Taking the metaphor of the signature in a broader figurative sense, one could suggest that Isaac's work also bears his musical signature—namely in the personal style that his contemporaries tried to recognize and in some cases to characterize in words. Two authors who tried to capture the peculiar quality of Isaac's music are Paolo Cortesi and Heinrich Glarean. The latter's attempt is especially significant, since Glarean seems to attest to a new way of hearing and conceptualizing polyphony. Although it is hard to identify specifically which passages in Isaac's music he would have had in mind, the key to his appraisal seems to lie in a different way of conceptualizing the interplay of contrapuntal voices in contemporary music. To the extent that we can associate this with Isaac's musical signature, it would appear, once again, that this composer, more than any other, was at the forefront of some of the most significant developments in the music history of his time.
For Giovanni Zanovello
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