 It might seem that, since musical works are ontologically multiple, once we have figured out their true nature, we will know what relation holds between the work and its instances. However, since the fundamentalist debate is about the basic ontological category to which works belong, resolving that debate may leave open many questions about the instantiation relation. For instance, is the use of a harpsichord required to instance Bach’s Brandenburg Concerto No. 5 in performance? Would producing harpsichord-like sounds on a synthesizer do just as well? What about using another keyboard instrument from Bach’s time, or a modern piano? Learning that musical works are, say, eternal types will not necessarily help settle this issue of “authentic performance”, which is perhaps the most discussed ontological issue, of interest to philosophers, musicologists, musicians, and audiences alike.