This is from a project I’m working on, and I thought you might find these two recordings to make an interesting comparison.
This is the Siciliano from J.S. Bach’s E-major flute Sonata, played on two very different simple-system flutes, my 6-key Hamilton, and my old 8-key German flute.
There have been many interesting discussions on why the old flutes were tuned the way they were. I think you may find these recordings illuminating: listen to the intervals on the German flute verses the modern Irish flute when playing in E-major and C-sharp minor.