"Very little has been written on the acoustics of harps, except for Firth's short 1977 paper on the Scottish clarsach. As a physicist and amateur harp builder I have a made a start on extending Firth's work, using a small Celtic harp and a larger Lever Harp - both home-made - and a Salvi Concert Pedal-Harp. I also build on the work of Weinreich on piano strings, Gough on violin strings, and a recent general analysis of vibrating strings by O'Reilly and Holmes. My talk will start with an overview of harp evolution and diffusion, with some discussion of basic mechanical issues, then I will review my own measurements, and will end on where this work is heading."