IME, not only the choice of material, but how the material is processed has a significant effect on the sound.
Again IME, the descending order of sonic quality is: 1 machined from solid billet, 2 extruded into approximate shape then machined, 3 forged, 4 vacuum or pressure-cast, 5 sand cast.
I should also point out that the phosphor bronze alloys used in machining are different from those used for casting (higher tin and lead content).
hth, jonathan carr
Again IME, the descending order of sonic quality is: 1 machined from solid billet, 2 extruded into approximate shape then machined, 3 forged, 4 vacuum or pressure-cast, 5 sand cast.
I should also point out that the phosphor bronze alloys used in machining are different from those used for casting (higher tin and lead content).
hth, jonathan carr