Scope and Contents This undated letter from John Donaldson to H. H. Dibdin, and written from Marchfield, discusses the adjustment and tuning of an organ, and denies that Sir George Clerk had advocated 'the absurd perfect third system' stating, 'Until the valves were equally opened it was quite impossible to know, precisely, what kind of temperament Mr. Hill had adopted for the Music Hall organ. When I tried it with Sir G. Clerk we found one stop in tolerable tune - I say tolerable, but even in that stop many...