Different materials have different natural vibration frequencies.
Titanium has a very dynamic sound. Its frequency response boosts higher midrange, giving a brighter sound. It is not difficult to machine, the hardness is like steel.
Aluminium has dryer sound as it enhances treble. Steel has stronger bass but mainly neutral. Tungsten has pinpoint focus and tighter bass. The list goes on, just as different woods and acrylic.
The best result is often a combination of different materials.